Programming and Web Development Tutorials

Accessing Directories in C/C++ Part II in C++ Tutorials

gabehabe — Fri, 08 Aug 2008 12:14:43 -0600

Working with directories Part II
Creating and removing directories!

First off, if you haven't already, I suggest you read Part I of this tutorial, since a function which I have written will utilise everything that is taught in that tutorial.

Next, take a look at this snippet which I wrote. It should make sense, if you understood Part I.

Good, now we're ready to start. I will be making use of that snippet in this tutorial, to show our progress.

Let's begin!

What are we going to cover in this tutorial?
Well, in Part I, we learned how to access a directory, using DIR* and dirent*
Now, in this tutorial, we will learn how to use some (simple) functions, which perform the following tasks:

Creating a new directory
Deleting a directory
Changing our active directory
Getting the whole path of the current directory

As with Part I, this is compatible with both C++ and C, therefore I will provide the main code in C, and convert it to C++ at the end. (Again, the only difference is console output)

First off, I'm going to give you the bulk of the code. This is the includes and the function which we will use to list the contents of the current directory:
[code=cpp]#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>

void listdir (const char *path);

int main ()
{
// example code will go here
return 0;
}

void listdir (const char *path)
{
// first off, we need to create a pointer to a directory
DIR *pdir = NULL; // remember, it's good practice to initialise a pointer to NULL!
pdir = opendir (path); // "." will refer to the current directory
struct dirent *pent = NULL;
if (pdir == NULL) // if pdir wasn't initialised correctly
{ // print an error message and exit the program
printf ("\nERROR! pdir could not be initialised correctly");
return; // exit the function
} // end if

while (pent = readdir (pdir)) // while there is still something in the directory to list
{
if (pent == NULL) // if pent has not been initialised correctly
{ // print an error message, and exit the program
printf ("\nERROR! pent could not be initialised correctly");
return; // exit the function
}
// otherwise, it was initialised correctly. let's print it on the console:
printf ("%s\n", pent->d_name);
}

// finally, let's close the directory
closedir (pdir);
}[/code]
Creating a new directory
We can do this with a call to a simple function, call mkdir() like so:
[code=cpp]mkdir (".\\dream.in.code");[/code]
The . represents our current directory (by default, this is the directory from which the program was launched)

So, now we have created a new folder called "dream.in.code"

Getting the current directory
This can be done with a call to a function called getcwd() like so:
[code=cpp]printf ("Currently viewing:\n%s\n", getcwd(NULL,0));[/code]As you can see, we are outputting the return value of the function, which is a string referring to the path of the current directory. Note that the function accepts two parameters. We aren't going to go into detail right now, since this is just the basics of directory access, but just remember that you can pass NULL,0 to it to get the current path /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

Just to clarify that our dream.in.code folder has been created successfully, let's list the contents of our current directory, using my snippet:[code=cpp]listdir (".");[/code]Remember, . refers to the current path. Now, if you run the program, you should see a folder called dream.in.code at the bottom of the list. Now let's move into that folder!

Changing the active directory
Again, all that we need to do is make a call to a simple function called chdir() I'm going to do this, and call the getcwd() and listdir() functions for the output, to keep output clear.[code=cpp] chdir (".\\dream.in.code");
printf ("\nCurrently viewing:\n%s\n", getcwd(NULL,0));
listdir (".");[/code]NOTE: At this point, the output from this listdir() call should just be:
.
..
because . refers to the current directory, and .. refers to the parent directory. There will be nothing else, since we have not put anything into this folder.

Now, just for clarity, I'm going to move back a folder, using .. and output the current path, like so:[code=cpp] chdir ("..\\"); // move back one
printf ("Currently viewing:\n%s\n", getcwd(NULL,0));[/code]Finally, let's remove our "dream.in.code" directory.

Removing a directory
Yet another single function call! Isn't this directory stuff easy? Now, to remove a directory, we can make a call to rmdir() like so:[code=cpp] rmdir (".\dream.in.code");[/code]And finally, I'll make another call to my snippet in order to reveal on the console that our directory has gone:[code=cpp] listdir (".");[/code]

And that's all there is to it!

Why not go down to the local bar and try to pick up some girls with your super cool new directory accessing skills? I'm sure they'll be impressed! /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

Now for the final code again!

C CODE![code=cpp]#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>

void listdir (const char *path);

int main ()
{
if (!mkdir (".\\dream.in.code"))
{
printf ("mkdir() unsuccessful. Terminating...");
exit (3); // exit after a 3 second pause
} // otherwise, it was created, so we can continue
printf ("dream.in.code folder created successfully!");
printf ("Currently viewing:\n%s\n", getcwd(NULL,0));
listdir (".");
printf ("\nMoving into our newly created directory");
chdir (".\\dream.in.code");
printf ("\nCurrently viewing:\n%s\n", getcwd(NULL,0));
listdir (".");
chdir ("..\\"); // move back one
rmdir (".\dream.in.code");
listdir (".");

return 0;

}

void listdir (const char *path)
{
// first off, we need to create a pointer to a directory
DIR *pdir = NULL; // remember, it's good practice to initialise a pointer to NULL!
pdir = opendir (path); // "." will refer to the current directory
struct dirent *pent = NULL;
if (pdir == NULL) // if pdir wasn't initialised correctly
{ // print an error message and exit the program
printf ("\nERROR! pdir could not be initialised correctly");
return; // exit the function
} // end if

while (pent = readdir (pdir)) // while there is still something in the directory to list
{
if (pent == NULL) // if pent has not been initialised correctly
{ // print an error message, and exit the program
printf ("\nERROR! pent could not be initialised correctly");
return; // exit the function
}
// otherwise, it was initialised correctly. let's print it on the console:
printf ("%s\n", pent->d_name);
}

// finally, let's close the directory
closedir (pdir);
}[/code]
C++ CODE![code=cpp]#include <dirent.h>
#include <cstdio> // for the snippet
#include <iostream> // for output

void listdir (const char *path);

int main ()
{
if (!mkdir (".\\dream.in.code"))
{
printf ("mkdir() unsuccessful. Terminating...");
exit (3); // exit after a 3 second pause
} // otherwise, it was created, so we can continue
std::cout << "dream.in.code folder created successfully!"
<< "Currently viewing:\n%s\n" << getcwd(NULL,0);
listdir (".");
std::cout << "\nMoving into our newly created directory";
chdir (".\\dream.in.code");
std::cout << "\nCurrently viewing:\n%s\n" << getcwd(NULL,0);
listdir (".");
chdir ("..\\"); // move back one
rmdir (".\dream.in.code");
listdir (".");

std::cin.get (); // pause for input
return EXIT_SUCCESS; // program was executed successfully

}

void listdir (const char *path)
{
// first off, we need to create a pointer to a directory
DIR *pdir = NULL; // remember, it's good practice to initialise a pointer to NULL!
pdir = opendir (path); // "." will refer to the current directory
struct dirent *pent = NULL;
if (pdir == NULL) // if pdir wasn't initialised correctly
{ // print an error message and exit the program
printf ("\nERROR! pdir could not be initialised correctly");
return; // exit the function
} // end if

while (pent = readdir (pdir)) // while there is still something in the directory to list
{
if (pent == NULL) // if pent has not been initialised correctly
{ // print an error message, and exit the program
printf ("\nERROR! pent could not be initialised correctly");
return; // exit the function
}
// otherwise, it was initialised correctly. let's print it on the console:
printf ("%s\n", pent->d_name);
}

// finally, let's close the directory
closedir (pdir);
}[/code]

Accessing directories in C/C++ Part I in C++ Tutorials

born2c0de — Fri, 08 Aug 2008 05:19:22 -0600

QUOTE

exit (3); // pause for three seconds before exiting

Which header file is exit defined in?

As far as I know, the one defined in stdlib.h takes a status parameter, and doesn't pause for 'status' seconds when called.

Creating custom .h files and adding them to a project in C++ Tutorials

gabehabe — Wed, 06 Aug 2008 14:41:45 -0600

Creating a Project in C/C++
Using various filetypes:
.h .cpp

This is a little IDE specific but I'll make it as general as possible.

This is quite specific, but it can be generalised. Basically, when you create a new project, you should already have a .cpp file added to it, since this is where the main loop goes. This file is often called main.cpp

Now, to add a new file, most IDEs will require you to go to File>New. You should then see an option called something like "Header file." If not, then it is most likely File>New>file...

Now, make sure that it is a .h file that you are creating, give it a name, and click next/OK. Follow the wizard until you are returned to the coding view, and you should now be working in a header file (WhateverYouCalledIt.h)

First off, I'm going to add some header guards. This is basically to prevent the file being included more than once, which can cause errors (saying that things have already been declared, and are now being redeclared)

The easiest one is a simple one-line tool. However, it's not used very often.
[inline]#pragma once[/inline]

The more common method is to use [inline]#ifndef[/inline] like so:
[code=cpp]#ifndef MYHEADER_H_INCLUDED
#define MYHEADER_H_INCLUDED
// header content goes here
#endif[/code]This looks more confusing than it is. let's break it down a little.

A header file is most often used to contain variable declarations, function prototypes, and class declarations. In this example, I'm just going to use a few variables, because you may not yet be at a level of writing functions/classes.

Here is a very basic header file: [code=cpp]#ifndef MYHEADER_H_INCLUDED
#define MYHEADER_H_INCLUDED

int a; // declare an int
double b; // declare a double
char c; // declare a char

// notice that I haven't assigned any values here?
// we do that next, in a cpp file

#endif[/code]Now it's time to make a .cpp file to define everything in that header file. So, go to File>New>File... again. This time, however, instead of selecting .h we're selecting .cpp
Give it the same name as the header file. This will make it easier to manage later on. /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

Let's include our header file, and assign some stuff to our variables:[code=cpp]#include "myheader.h"

a = 4;
b = 20.2994;
c = 'D';[/code]Pretty simple, huh? That's because we're not really learning any new code. All that we're doing is breaking up some code into manageable files. It seems a little pointless here, but it's much better to have a few files with a few hundred lines each than one big file with thousands of lines. It simply makes it easier to manage!

Now to write the code for our main.cpp
All we need to do is include our header file, and the contents of the cpp file will be included for you.
This is main.cpp:[code=cpp]#include <iostream> // input/output stream
#include "myheader.h" // use " " instead of < > so the compiler knows that it's a local header file

using namespace std;

int main ()
{
cout << a << endl << b << endl << c;
cin.get ();
return EXIT_SUCCESS;
}[/code]
There are no scoping issues, since these variables have simply been dragged into the program at compile time.

Happy coding! /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

C++ Namespaces Part I in C++ Tutorials

gabehabe — Wed, 06 Aug 2008 13:56:08 -0600

Working with namespaces

What is a namespace?
A namespace is basically a container for a group of variables/functions etc. I can pretty much guarantee everyone reading this tutorial has already used a namespace in C++ programming. Think of a line that usually comes at the top of a beginner program:
[inline]using namespace std;[/inline]
This is the standard namespace. It's got the definitions of a lot of neat stuff in there.

Why should I use a namespace?
Namespaces are pretty neat. We use them to contain a group of data. Also, it makes it possible to have more than one variable with the same name. One of which is in the namespace, one which isn't. This will be explained later on.

When writing a namespace, there's nothing you need to include. A namespace is a standard container.

I'm gonna put my namespace in a seperate header file, just to save confusion.

Let's start with our header guards. I'm gonna call the header file "namespace.h" but you can call it whatever you like.
Also, I'm just gonna define it in the .h file. Granted, this is bad habit, but this is just a quick example.

[code=cpp]#ifndef NAMESPACE_H_INCLUDED
#define NAMESPACE_H_INCLUDED[/code]
Now we're ready to start writing a namespace. I'm gonna write a simple "math" namespace, since I've used something similar in a few posts to explain it already, and the people who I wrote it for found it quite useful.

There isn't too much to writing a namespace, but it's a useful skill. There isn't too much to break it down into, so I'm gonna post up a simple namespace here. This is namespace.h:
[code=cpp]#ifndef NAMESPACE_H_INCLUDED
#define NAMESPACE_H_INCLUDED

namespace math // define a namespace called math
{
namespace numbers // an example of a nested namespace
{ // define some variables within our math::numbers namespace
int one = 1;
int two = 2;
int three = 3;
int four = 4;
int five = 5;
int six = 6;
int seven = 7;
int eight = 8;
int nine = 9;
} // end of nested namespace

// define some functions within our math namespace
int add (int x, int y) {return x + y;}
int subtract (int x, int y) {return x - y;}
int divide (int x, int y) {return x / y;}
int multiply (int x, int y) {return x * y;}
}

#endif // NAMESPACE_H_INCLUDED[/code]
As you can see, I've even made a nested namespace. You can nest namespaces as far as you like, but it seems a little pointless to have something as long as:
[inline]namespace1::namespace2::namespace3::namespace4::x[/inline] just to access a variable named x.

And now that I've said that, you're probably thinking "what's this :: operator that this fool uses?"
The :: operator is known as the scope operator, and it is used to access certain things from within a namespace. The most common, which you may have seen before is something like:
[inline]std::cout << "something";[/inline]
This line basically means that cout is defined in the std namespace. Makes sense, right?

Onwards to the various methods of accessing a namespace! This can be done with various methods.
There are three methods of accessing something from within a namespace. I'm gonna use the std namespace as an example here:

[inline]using namespace std;[/inline] This means that we want to be using everything which is defined within the std namespace
[inline]using std::cout;[/inline] This means that we only want to use cout from the std namespace
This last method doesn't require the using keyword. We use it whenever we want to access something from the namespace. Example:
[code=cpp]#include <iostream> // input/output stream

int main ()
{
std::cout << "Enter something!" << std::endl;
char input;
std::cin >> input;
std::cout << "You entered: " << input << "!" << std::endl;
std::cin.get (); // pause
return EXIT_SUCCESS;
}[/code]

Notice how we had to prefix every use of any std feature with std:: ? This can become tedious, which is why we have the using keyword! /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

Now for our main.cpp file, which is used to demonstrate everything we've learned so far:
[code=cpp]#include <iostream>

#include "namespace.h"

// using a namespace
using namespace math; // using everything from the namespace called numbers
// (our nested namespace)

// using individual members of a namespace
using std::cout; // use cout from the std namespace specifically
using std::cin; // use cin from the std namespace specifically
using std::endl; // use endl from the std namespace specifically

int main ()
{
cout << math::add (numbers::three, numbers::two) << endl;
// note: if we weren't using the math namespace, we would have to prefix three and two with:
// math::numbers::three and math::numbers::two
// this is why it's kind of advisable against using huge nested namespaces!

// now, since we need to access two through numbers::two we can still have another variable called two
// because of the scope.
int two = 771123;
// now let's output both "two" variables and see what we get
cout << "two = " << two << endl
<< "numbers::two = " << numbers::two;

cin.get ();
return EXIT_SUCCESS;
}[/code]

You can also create namespace with no name, which I will write about in a part II of this tutorial.

Happy coding!

How to create a Mail Merge in Word 2007 in Windows Tutorials

RodgerB — Wed, 06 Aug 2008 02:23:00 -0600

I had to write a tutorial as a part of my assessment in one of my I.T classes, so I thought I'd share it with you guys.

The Word Document attached looks a lot better then this tutorial, purely because of the lack of control I have with BBCode. I do suggest you read it as it is formatted a lot clearer than it is with the forum software. For those too lazy to read it, continue reading.

[attachmentid=7900]

How to create a Mail Merge

Microsoft Word has the option of merging information from a database (such as Names, Addresses) into formal letters. This option is called a Mail Merge. This step-by-step tutorial will explain the following Mail Merge concepts:

How to create a recipient list for use in a Mail Merge
How to import an address list for use in a Mail Merge
How to greet a recipient in a document
How to display a recipient�s address in a letter
How to insert an individual field into a letter
Finishing the Mail Merge

How to create a recipient list for use in a Mail Merge

Figure 1.1: The New Address List Dialog

Creating a recipient list is simply a matter of clicking the �Mailings� tab on the office ribbon, clicking the Select Recipients button and selecting the �Type New List� option from the drop-down list.

You will be presented with a �New Address List� dialog box (see Figure 1.1). By default, you have the options of providing a wide variation of information about recipients, such as names and contact details.

Type your list of recipients into the table and click the Ok button to close the window. A dialog will appear, prompting you to tell Microsoft Word where to save your new address list so we can access it easily in all documents. Give it an appropriate name and click the save button.

Tip: If you need to add additional columns to your address list, select the �Customize Columns...� option in the bottom-left corner of the window.

How import an address list for use in a Mail Merge
To actually use the Mail Merge function, we will need to import a recipient list. We have already created one in the previous step; so again, select the �Mailings� tab on the office ribbon and click the �Use Existing List� button. A dialog will appear prompting you to locate your address list. Select the address list and click Open.

You will notice some buttons that were previously disabled on the ribbon are now enabled as a result of this operation; this is because Microsoft Word now knows the current document is working with a Data Source.

Tip: It is not a good idea to import an address list on removable storage devices. When Windows detects a removable storage device, it allocates it a drive letter based on the ones that aren�t being used on the current computer. What this means to you, is that your document may not properly find the address list file if its path keeps changing.

How to greet a recipient in a document

Figure 1.2: The Insert Greeting Line Dialog

Greeting a recipient in a document is easy. First select the �Mailings� tab on the office ribbon, and then select the Greeting Line button. A dialog will appear titled �Insert Greeting Line� (figure 1.2).

This dialog will allow you to change the format of the greeting, the greeting line for recipients Microsoft Word doesn�t have data for and a preview of what the greeting will look like in your document.

How to display a recipient�s address in a letter
Displaying a recipient�s address is much the same deal as greeting a recipient in a document. Select the �Mailings� tab on the office ribbon and click on the Address Block button.

A dialog will appear, prompting you to choose the format of the recipient�s name, whether to insert the company name or not, the option of including the postal address and a preview of how the address block will appear in your document. Modify these options to your liking and click ok.

How to insert an individual field into a letter

Figure 1.3: The Insert Merge Field Dialog

Sometimes you may need to insert a name or email address out of the blue into your document (or anything else you can think of that you entered into the address list). This can be performed by using the �Insert Merge Field� option.

Click the �Mailings� tab on the office ribbon, and select the top half of the �Insert Merge Field� button. A dialog will appear (see figure 1.3), giving you an option of selecting a variety of fields.

When you have found the type of field you would like to insert into your document, select it in the list and click �Insert�.

Finishing the Mail Merge
To finish the mail merge, click the �Mailings� tab on the office ribbon and select the �Finish & Merge� button. It will give you the option of editing the individual documents, printing the documents or sending the document as an email.

Selecting any of the three options will present you with a dialog asking which records in the address list you would like to use. Selecting �All� will perform the operation on all records in the address list.

Conclusion
I hope this tutorial has enlightened you as to the many benefits of using a Mail Merge, and how it can make writing letters to multiple recipients much less work.

Determining the distance between two points in PHP Tutorials

rjolitz — Sun, 03 Aug 2008 03:11:00 -0600

Hello!

In this tutorial we are going to tackle a rather basic problem. How to determine the distance between two points on an X,Y grid.

Our starting points for the purpose of this tutorial will be (1,-10) and (15,-20). For our code we will be setting these values into variables but you can also accept them from a form as well as pull them from a MySQL database depending on your project.

First we'll set our variables and give them a value:

CODE

<?php

// first coordinate set (1,-10)
$x1 = 1;
$y1 = -10;

// second coordinate set (15,-20)
$x2 = 15;
$y2 = -20;

The next step is to subtract the x coordinate of the first set from the second set. We also need to do the same for the y coordinates. Then both values need to be squared. This is easily accomplished using PHP's [il]pow(x,y)[/il] function. X equals the value to be raised, y equals the power to raise it by. If you want to know the value of 10 to the 9th power it would like [il]pow(10,9)[/il]

CODE

$x = ( pow($x2,2) - pow($x1,2));
$y = ( pow($y2,2) - pow($y1,2));

The last step is to add these two values and find the square root.

CODE

$distance = ( sqrt($x + $y) );

For our example the final answer is 22.891046284519. If you want to round this value to nearest full number you can use the [il]round()[/il] function, which will round the number up or down. If you want to round to a certain number of decimal places, you can specify that such as [il]round(11,3)[/il]

[il]round($distance)[/il] returns the value: 23

[il]round($distance,2)[/il] returns the value: 22.89

Putting it all together our code looks like:

CODE

<?php

// first coordinate set (1,-10)
$x1 = 1;
$y1 = -10;

// second coordinate set (15,-20)
$x2 = 15;
$y2 = -20;

$x = ( pow($x2,2) - pow($x1,2));
$y = ( pow($y2,2) - pow($y1,2));

$distance = ( sqrt($x + $y) );

// Round to nearest full number

$roundtofull = round($distance);
$roundto2places = round($distance,2);

?>

This tutorial is really basic in showing how to determine distance, but I do hope you found it useful.

Make a Bomb in Photoshop Tutorials

gbertoli3 — Sat, 02 Aug 2008 14:49:18 -0600

First start by creating a new document (500 x 500). After that select the type(text) tool. Choose Wingdings for the font and 400 for the font size see figure 1 for more details.
Figure 1

Type a capital M. If you have done this right there should be a bomb shape for your text, see figure 2 for example. Duplicate the text layer and then rasterize it by going to Layer->Rasterize->Type, and name this layer to bomb.
Figure 2

Then make a duplicate of the bomb layer two more times, name it fuse, and sparks.

Select the bomb layer by ctrl clicking the layer. Delete the sparks with your wand tool, start by alt clicking the black sparks, this will deselect the sparks. Press Shift + Ctrl + I to inverse the selection, then press delete, this will delete the sparks from the layer. Still on the bomb layer Ctrl + Click the layer to select it once again. You can use any way you feel like for this next part. First Alt + Click & Drag a selection around the fuse. If you did this correctly only the round part of the bomb and the piece that connects the bomb with the fuse will be selected. Shift + Ctrl + I again to inverse the selection, press delete to delete the selection. see figures 3 and 4 for details.

Figure 3

Figure 4

Then add a gradient overlay to this layer, figures 5 & 6 have gradient settings. After add an inner glow to the layer, figure 7 has glow settings.

Figure 5

Figure 6

Figure 7

This is what you should have.

Figure 8

Do the exact same thing on the spark and the fuse layer only for the fuse layer have only the fuse selected, for the spark layer only the sparks selected, after that we will apply some styles to those layers.

Figure 9

Now go to File->New, set the height & width properties to 8 pixels. Select the rectangular marquee tool and drag four pixel while holding down shift, seen in figure 10.

Figure 10

Fill the selection with white, move the selection to the right 4 pixels by hitting the right arrow key 4 times, fill the selection with black, press the down arrow key 4 times and fill it with white, then the left 4 times and fill with black, seen in figure 11.

Figure 11

Go to Edit->Define Pattern. Go back to the bomb document and select the fuse layer. We will add a few layer styles to it. First layer style is a gradient overlay, see figure 12 & 13. Then we will add a pattern overlay, the pattern will be the pattern that we just created previously, see figure 14. The last layer style we will add to the fuse layer is an inner glow, see figure 15.

Figure 12

Figure 13

Figure 14

Figure 15

This is what you should have, see figure 16.

Figure 16

We are almost done!

Now select the spark layer, we will be adding a gradient overlay, see figures 17 & 18.

Figure 17

Figure 18

Finished!

This is what you should have.

Have Fun!
Don't Forget I Have Included the PSD File [attachmentid=7850] & [attachmentid=7851].

Zen and the Art of Debugging C/C++ Programs in Visual Studio in C++ Tutorials

born2c0de — Sun, 03 Aug 2008 01:29:11 -0600

Approved.
Well done jwwicks.

Looping in Java Tutorials

Locke37 — Thu, 07 Aug 2008 17:20:50 -0600

Oh! GOOD CALL

I'll edit it right now, while I'm thinking about it.

EDIT: Crap, it's too old to edit, but I've got a plan B. /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

Introduction to Designing Classes II in Java Tutorials

Locke37 — Wed, 30 Jul 2008 17:22:14 -0600

Well, this is me second tutorial on designing classes with static methods. I'm gonna start you off with a very basic example: the Math class.

This class has methods that do mathematical calculations...I know...duh. Well, the methods of the Math class are static, meaning you don't have to instantiate an object to call them. You can simply call them like this.

[code=java]Math.METHOD(parameters_used);[/code]

You DON'T have to do this:

[code=java]Math mathObject = new Math();

mathObject.METHOD();[/code]

You don't HAVE to do it that way...but you can, but no one I know does that. /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

Well, we'll make a method that does a very simple calculation. We'll make an [il]addition()[/il] method.

[code=java]class OurMath
{
public static int addition(int a, int /cool.gif" style="vertical-align:middle" emoid="B)" border="0" alt="cool.gif" />
{
int sum = a + b;

return sum;
}
}[/code]

Notice how we declare our int return type for the method. This makes it so we can assign it to an int variable in a main method or something.

Also notice the int variables in the parentheses. These are called 'parameters'. These are what's going to be included in the method when it's called.

It's going to be called like this.

[code=java]int number = OurMath.addition(1, 3);[/code]

Well, anyone know what [il]number[/il] is going to equal after that? That's right! Four!

You HAVE to call the method with 2 parameters. If you call it any other way, you're going to going to get a compile error saying something along these lines. [il]cannot find symbol: method addition(int)[/il]

static Class Variables

Well, back again to the Math class. It has 2 double variables, E, and PI.

[code=java]class Math
{
static double E = 2.718...;
static double PI = 3.141596535...;
}[/code]

This is how we declare static (AKA "class") variables. Let's go back to our class...

[code=java]class OurMath
{
static int five = 5;

public static int addition(int a, int /cool.gif" style="vertical-align:middle" emoid="B)" border="0" alt="cool.gif" />
{
int sum = a + b;

return sum;
}
}[/code]

Well, now we can access our [il]five[/il] variable through doing this.

[code=java]int ourVariable = OurMath.five;[/code]

The main reason of using static is to make non "object"-ive data or methods.

Hope this tutorial helped anyone that needed it! /biggrin.gif" style="vertical-align:middle" emoid=":D" border="0" alt="biggrin.gif" />

Intro to Designing Classes in Java Tutorials

Locke37 — Tue, 29 Jul 2008 15:28:24 -0600

Well, if you're reading this, you most likely do not have a lot of Java experience. No offense to anyone that reads this that DOES have a bit of experience, but this is just a basic concept.

Well, let's get started. /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

Now then, classes that have a need of objects...this is what we are going to make.

I'll start with an example that some people like, a Character (for a game) class. Let's start with the basic header for our class and a constructor.

[code=java]class Character
{
public Character()
{
}
}[/code]

Well, this is not a very good class yet, since we don't have any data...or methods...or anything besides a constructor...so let's add some! A Character needs HP and MP, right?

[code=java]class Character
{
private int HP;
private int MP;

public Character()
{
}
}[/code]

Notice how we declare these private. Declaring them private makes it so that they can only be accessed and/or changed by members of it's own class. (AKA the methods)

Well, now we have data, but it's never initialized, let's add that real quick. /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

[code=java]class Character
{
private int HP;
private int MP;

public Character(int hp, int mp)
{
this.HP = hp;
this.MP = mp;
}
}[/code]

Notice the this keyword. This is a pointer to the object that is calling the method. [il]OBJECT.method();[/il], in that case, the this keyword will reference [il]OBJECT[/il].

Now we have some HP and MP. Hooray! But now we need some methods to access these variables, right? RIGHT, Locke!

[code=java]class Character
{
private int HP;
private int MP;

public Character(int hp, int mp)
{
this.HP = hp;
this.MP = mp;
}

public int getHP()
{
return this.HP;
}

public int getMP()
{
return this.MP;
}
}[/code]

Well, now we have some methods to access our attributes. Notice the return type before the method heading...it NEEDS to be there, so that the method knows what it's supposed to be returning. The return type is always the same as the variable type in basic return methods like these, that just access and tell you what the variable value is.

So if we have something like this...

[code=java]private String name;

public String getName()
{
return this.name;
}[/code]

Well, with our private declaration, we can't change our HP or MP values, only access them with our methods, so let's add some [il]set[/il] methods.

[code=java]class Character
{
private int HP;
private int MP;

public Character(int hp, int mp)
{
this.HP = hp;
this.MP = mp;
}

public int getHP()
{
return this.HP;
}

public int getMP()
{
return this.MP;
}

public void setHP(int newHP)
{
this.HP = newHP;
}

public void setMP(int newMP)
{
this.MP = newMP;
}
}[/code]

We MUST have parameters in our [il]set[/il] methods, or Java doesn't know what to set the values to. Notice the void keyword in the method heading...this means the method doesn't return anything. It doesn't need to, since it's just changing values.

Well, this is just a very basic tutorial in designing Object methods/classes. If you want to know how to make Static classes, you can PM me if my next tutorial does not get approved.

Bye! /biggrin.gif" style="vertical-align:middle" emoid=":D" border="0" alt="biggrin.gif" />

AS 2.0 Basics 4 - Functions in Flash Tutorials

BetaWar — Mon, 28 Jul 2008 17:04:48 -0600

Functions make doing things multiple times with different values very fast and easy, however if you haven't used functions in the past they can be quite a hassle to get into and understand.

Hello Function new to the world

We will start by creating a simple function that will trace (output) [inline]Hello Function![/inline]. This is accomplished by creating a function which you define like so [inline]function FUNCTION_NAME()[/inline]. For our current purposes we will name the functio [inline]hello_func[/inline] like so: [inline]function hello_func()[/inline]. The [inline]()[/inline] is where you typically place any parameters (variables) that you are passing into the function for its use, however for the moment we will be passing in no parameters so it is left blank. Now we just need to tell the code where the function starts and ends and what to do. This is accomplished with the following code.

CODE

function hello_func(){
trace("Hello Function!");
}

NOTE - This is all the code needed to declare our function!

Now we have a working function, but how do we get it to run?
This is a fairly simple answer, you call the function. This can be done by typing the function name and then the () with any parameters needed (in this case it is none). [inline]hello_func();[/inline]

OUTPUT - [inline]Hello Function![/inline].

Returning a value
Functions are also usefule because they can return a value. Say you wanted to know what 2+2 was; a function could tell you. You declare the function in the same way as above, but this time we need to change the contents of the function. We no longer need the [inline]trace("Hello Function!");[/inline] so we can delete that.

NOTE - For our purposes we will call this function adding (because add is a keyword in AS 2.0).

Then we place a return statement that returns the sum of 2+2 (4).

CODE

function adding(){
return 2+2;
}
trace(adding());

After we have finished the function [inline]}[/inline] we will have the script trace the value returned.

OUTPUT - [inline]4[/inline].

Passing Parameters
Functions also allow you to pass parameters into them. This can be quite useful (taking adding as an example) if you want to know the sum of 2 numbers that aren't going to be available hard-coded into the function.

You need to start off by telling the function what to expect, this is accomplished as such: [inline]function FUNCTION_NAME(PARAM_1, PARAM_2)[/inline]

We will now begin rewriting our adding function to add different numbers and output the sum. To start out we need to have the function looking for things to add together. Our new function will be coded as so:

CODE

function adding(a:Number, b:Number){
return a+b;
}

This takes 2 numbers (say 1 and 3) and adds them together then returns the value (1+3 = 4). Passing parameters into i is simple too: [inline]adding(1, 3);[/inline].

Our new code looks like this:

CODE

function adding(a:Number, b:Number){
return a+b;
}
trace(adding(1, 3));

OUTPUT - [inline]4[/inline].

Beginning Defensive Programming so you don't error out all the time
Defensive programming (in this case) is making sure that you don't allow undefined variables to be sent into the function. If we were to call adding like so: [inline]trace(adding(1, ));[/inline] the output looks like so:

QUOTE(Flash 8 Output window)

**Error** Scene=Scene 1, layer=Layer 1, frame=1:Line 1: Parameter name expected
function adding(var a:Number, var b:Number){

**Error** Scene=Scene 1, layer=Layer 1, frame=1:Line 4: Unexpected ')' encountered
trace(adding(1, ));

Total ActionScript Errors: 2 Reported Errors: 2

This isn't what you want to have happen if you are going to be putting this out on the web for people to use. So, how do you cover the bases?

It is a little easier than you would think, however Flash 8 (AS 2.0) requires some differing methods than normally used in programming languages. You have to use if statements (sadly, AS 2.0 doesn't allow you to set initial values for parameters being sent to functions).

For our case we will be checking if the numbers are set or not. If they aren't we will set them to 0, otherwise we will leave them as they are.

CODE

if(!a){
a = 0;
}
if(!b){
b = 0;
}

Now we just place this in the top of our function and we have some basic defensive programming going on.

CODE

function adding(a:Number, b:Number){
    if(!a){
        a = 0;
    }
    if(!b){
        b = 0;
    }
      return a+b;
}

If we were to call adding with only 1 variable (or none) it would now return an answer and not error out:
[inline]trace(adding());[/inline] OUTPUT - [inline]0[/inline].
[inline]trace(adding(1));[/inline] OUTPUT - [inline]1[/inline].
[inline]trace(adding(0, 2));[/inline] OUTPUT - [inline]2[/inline];

REALIZE - This is not perfect, if the user inputs something like ( , 2) it will still error out.

Returning Multiple Values because one isn't good enough
If you have multiple variables that are found in a function and want them all to be returned you may think that comma (,) delimiting them will do the trick (as it does in some languages). However, Flash and AS 2.0 are not other languages and will not allow this. If you attempt to do it you will get the last value in the line of values to be returned and nothing else.

There is a way to get around this though and it can be quite useful; you must use arrays. In this example we will return a, b, and the sum of the 2.

CODE

function adding(a:Number, b:Number){
    if(!a){
        a = 0;
    }
    if(!b){
        b = 0;
    }
      return [a, b, a+b];
}

Now if we were to just trace out the returned values it wouldn't look right:
[inline]trace(adding(1, 2));[/inline] OUTPUT - [inline]1,2,3[/inline].

So you will need to split the array apart to be able to use various portions of it. This is done like so:

CODE

var returned:Array = adding(1, 2);
trace("The value "+returned[0]+" plus "+returned[1]+" equals "+returned[2]);

OUTPUT - [inline]The value 1 plus 2 equals 3[/inline].

The thing to remember when using arrays in AS 2.0 is that you can't name items in them, you just have to use the number index that thye have, so pay attention to the order you place values into an array.

NOTE - Arrays always start with index of 0.

Returning Multiple Values using objects instead of arrays
I understand that everyone wants to be able to name their values for easy access, I do too. Luckily, with the help of objects you can! Just create a new object and set its values equal to whatever you want (and use whatever name you want too) then return the object and you will be able to call its separate values without needing to memorize the index of each. It can look like so:

CODE

OUTPUT - [inline]The value 1 plus 2 equals 3[/inline].

NOTICE - I am not using indexes as in the array example above, but am using the varaibels names that I assigned to obj in the function. You can add and rename variables to be returned easily and quickly!

The End I hope that helps everyone understand how to use functions a bit more
See you next time /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

ArrayList vs. Static Arrays in Java Tutorials

Locke37 — Wed, 30 Jul 2008 16:42:44 -0600

No problem! /biggrin.gif" style="vertical-align:middle" emoid=":D" border="0" alt="biggrin.gif" />

Glad I could help!