Code Perspective

First off before we start, here are a couple of things you will need to get started:

1. Mac running the latest version of xcode – This can be found on your install disc for leopard or snow leopard.

2. Latest version of the iphone SDK – This can be found at developer.apple.com

Now we can get started. Once you have xcode and the iphone SDK installed, open up xcode(Macintosh HD > developer > Applications). Once you have xcode installed, from the menu bar select file > new project. You should see a windows like the this one.

Select window based application from the iphone application option on the left hand side of the window. Once you select the window based application, xcode will prompt you to save the project. I named my project “LabelTester” and saved it under my personal iphone projects directory. Once you save the project, an xcode window should open up and look something like this.

You should see a combination of files here in the browser in the code browser. The first should be the CoreGraphics.framework. This is just a set of files provided by Apple that have all the code relevant to the core graphics libraries in Cocoa. The second is the foundation.framework. This is the library set for the foundation framework which is basically all the classes like NSArray, NSString and other foundation objects. The next item should be LabelTester.plist. The plist, or preference list, is a set of XML attributes that control how the application is handled. For the sake of this tutorial, you won’t need to open the plist. The next item should be the LabelTester.app file, which is the executable for your application. Once your application is deployed, all files and resources in your project will be located inside your app’s .app file. The next file is the LabelTester.pch file. This file is the prefix header for your application. The LabelTesterAppDelegate.h file is the next file in the list. This file is the header file for your application delegate. This is the starting for your application, the app delegate is what’s run by your main.m file when you app is launched. The .h file is of course the header file, which is basically the interface file that the .m file will implement. The next file is of course the LabelTesterAppDelegate.m. This file is the implementation file for the app delegate header. Next is the main.m file. This file is the application launcher for your app. It basically runs the app delegate. The next file is the Main Window.xib file. Anything with a nib/xib file extension is classified as an interface builder file and you open these files in the Interface builder application. Finally, the UIKit.framework. This library is used to correspond to all the UI elements on the iphone(text fields, buttons, etc).

Let’s start by opening up our Main Window.xib to setup our interface. Start by dragging a button from the libraries window onto your main View. Rename that button by double clicking on the button and change it to say “Update Label!”. Next, grab a text field and drag it just above the button. Expand the text field to fit the majority of the screen. Select the textfield and go into the attributes tab and enter into the placeholder field, “Enter Text to update Label”. Once that’s finished, drag a label onto the main window and change the text from “label” to “Label to Update”. Once that’s done you can save the interface builder file by pressing (command + s) and switch your view back to your xcode project.

Open up the LabelTesterAppDelegate.h file and change the file to reflect the following code.

#import 
 
@interface LabelTesterAppDelegate : NSObject
{
    UIWindow *window;
	IBOutlet UITextField *textField;
	IBOutlet UIButton *button;
	IBOutlet UILabel *label;
	IBAction *updateButtonPressed;
}
 
@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UITextField *textField;
@property (nonatomic, retain) IBOutlet UILabel *label;
 
-(IBAction)updateButtonpressed:(id) sender;
 
@end

The first lines inside the curly braces will declare variables that we will be hooking up in Interface builder later. After the curly braces are closed, we have these property tags. These will allow us to have access to the objects and their data in the implementation file. After that we have an IBAction method declaration. This will eventually be hooked up to our button to run every time that our button is pressed. You can think of an IBAction method as an event handler in OBjective-C. Now let’s move onto our LabelTesterAppDelegate.m file and add the following method directly below out import statement.

#import "LabelTesterAppDelegate.h"
 
@implementation LabelTesterAppDelegate
 
@synthesize window;
@synthesize textField;
@synthesize label;
 
-(IBAction)updateButtonpressed:(id) sender
{
	//allocate a string and initialize it with the data from the text field
	NSString *string = textField.text;
 
	label.text = string;
}

Basically what we’re doing here is just creating that IBAction method that we declared in our interface file. Inside that method, we allocate a string to the value of our textField.text and then set the label equal to the string that we get from the textfield. That’s all the code we’ll need for now. Don’t forget to synthesize your objects below the implementation declaration in order to have access to the data you want. If you try and run this now, the application will run but will not function because the pointers in Interface Builder are not hooked up. So let’s go ahead and do that next. Save all your xcode files and open back up your Main Window.xib file in Interface Builder.

In order to setup a pointer in Interface builder, start by clicking on the application delegate and then the connections manager should appear. Beside each of the items that you created you should see a tiny circle. For each, click on the circle and drag the pointer to each of the elements in your window. This will create a pointer to that element. Now click on the button and then open it’s connection manager. Find the “touch up inside” connection and drag that pointer to the “file’s owner” section in the library and select “updateButtonPressed” when it appears. Once this is completed, you should see the connection screen look something like this.

That’s all folks, now if you run the application and enter some text into the text field, it will update the label to whatever text you entered. To download the whole project click here.

Cheers everyone and stay tuned for part 2!

Using a little knowledge of PHP and HTML you can build a simple log in system for your site. In order to correctly follow this tutorial you may want to have a good idea of basic HTML/PHP syntax as well as knowing some CSS. You should also have a basic understanding of how to create and use sessions($_SESSIONS) in PHP.

Alright let’s get started by just creating a basic log in window and place it in the center of the screen. First the log in window.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
	<head>
		<title>Sample Log In</title>
 
		<link rel="stylesheet" href="loginCSS.css" type="text/css" />
	</head>
	<body>
		<div id="outerLimit">
			<div id="container">
				<div id="innerLimit">
					<div id="loginBox">
						<form id="login" name="login" method="post" action="userAuth.php">
							<label for="username">Username:</label><br />
							<input type="text" id="username" name="username" size=40 /><br />
							<label for="password">Password:</label><br />
							<input type="password" id="password" name="password" size=40 /><br />
 
							<input type="submit" name="submit" value="Log In" />
						</form>
						<br />
					</div>
				</div>
			</div>
		</div>
	</body>
</html>

Next let’s move into a bit of the CSS. Basically we just want to create a window with a gray background so the fields are extremely easy to see. I called the CSS file in this case loginCSS.css but you can call it whatever you like as long as it’s referenced properly in the HTML section.

body
{
	background-color:white;
	min-height: 468px;
	min-width:552px;
	font-family:Helvetica;
}
 
a
{
	font-size:small;
}
 
#loginBox
{
	background-color: #e4e4e4;
	position:relative;
	top:25%;
	left:25%;
	width:300px;
	padding:15px;
}
 
#outerLimit
{
	height:100%;
	width:100%;
	display:table;
	vertical-align:middle;
}
 
#container
{
	position:relative;
	vertical-align:middle;
	display:table-cell;
	height:468px;
}
 
#innerLimit
{
	width:552px;
	height:468px;
	margin-left:auto;
	margin-right:auto;
}

As you can see, I just styled the page a little bit to make it a little bit easier for the user to use. Now that we have a basic page for the user to log in, we’ll also need a page, such as a dashboard, for the user to access when they enter in correct login criteria. In this case we’re just going to use a page that has a basic header telling the user they have logged in correctly. The page can look something like this.

 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
	<head>
		<title>Sample Log In</title>
 
		<link rel="stylesheet" href="loginCSS.css" type="text/css" />
	</head>
	<body>
		<h1>You are now logged in!</h1>
		<a href="logout.php">Log Out Here</a>
	</body>
</html>

As you can see I have also included a log out link just below the h1 tag. If a user logs into the system we also want them to be able to log out. Next we’re going to create the SQL for our database. For this tutorial I’ll be using MySQL, however Oracle or SQL Server could also be used.

Note: If you’re going to use a different database then the code to connect to the database will be slightly different.

DROP TABLE IF EXISTS 'testDB'.'user'
 
CREATE TABLE 'testDB'.'user'
(
	'username' VARCHAR(10),
	'password' VARCHAR(10)
);
 
INSERT INTO 'testDB'.'user'
(username, password)
VALUES
('admin', 'password'),
('guest', 'password');

This is just a very simple database table that contains only a username and password. This script could obviously be modified to accept further fields of to encrypt the password field to increase the security of your system. Things like that will be out of the scope of this tutorial however.

Now that we have our environment set up we can start to use PHP to get data from the forms and compare them with the database. For the this tutorial we will only be using the POST method of retrieving data from forms. Using GET is often not recommended when getting sensitive data such as usernames and passwords. As you can see from the log in window, we have used the POST method to get the data, and when the form is submitted we are calling the userAuth.php file. Let’s go ahead and create that file now.

This block of code we will be using to check to see if the fields are blank. If they are we want to send them back to the login.html file to log back in again using the header() function. Next we want to enter all the configuration information to connect to the database and use some PHP functions to protect our site from SQL injection errors.

/*Create the variables to hold the database information*/
 
$dbName = "testDB";
 
/*Table name that we're checking against*/
 
$dbTable = "user";
 
/*Database username*/
 
$dbUsername = "DBUsername";
 
/*Database Password*/
 
$dbPassword = "DBPassword";
 
$username = $_POST(['username']);
$password = $_POST(['password']);
 
/*This next block is to prevent SQL injection hacks*/
$username = stripslashes($username);
$password = stripslashes($password);
 
$username = mysql_real_escape_string($username);
$password = mysql_real_escape_string($password);

I have put in default values into the variables. Variables such as $dbTable and $dbUsername will be subject to change based on your database configuration. These values will need to be filled in with correct values from your system. Next we’re going to be connecting to the database and opening a connection.

/*Connect to the Database*/
 
$connection = @mysql_connect("localhost", $dbUsername, $dbPassword) or die(mysql_error());
 
/*Select the database you want to access*/
 
$db = @mysql_select_db($dbName, $connection) or die(mysql_error());
 
/*Select statement from the database to see if the user is in the system*/
 
$sqlQuery = "SELECT COUNT(*) FROM $table_name WHERE username = '$username'
AND password = password('$password')";
 
/*Create a variable to hold the results of the SQL query*/
 
$result = @mysql_query($sqlQuery, $connection) or die(mysql_error());
 
/*Check the number of rows returned from the query*/
 
$num = mysql_num_rows($result);

Now we’re getting to the user authentication section. We’re now going to see if the number of rows that was selected is anything but 0. In theory it should ever only come back with 1 or 0 rows, however in systems where users can multiple accounts it’s good to keep it to != 0.

/*If the number of rows is not equal to 0 then authenticate the user*/
 
if ($num != 0)
{
	session_start();
 
	//Create a session for the username and password
	session_register($username);
	session_register($password);
 
	if(!session_is_registered($username))
	{
		header("location:login.html");
	}
	else
	{
		//because the user is authenticated move them to the dashboard
		header("Location: home.html");
	}
}
else
{
	header("Location: login.html");
	exit;
}
?>

We then register a session and store the username and password in the session. If the session has been registered correctly then you can send the user to the home screen. If the session is not registered correctly for some reason we don’t want the users accessing the system, so we send them back to the login screen to attempt to log in again.

That’s it, an entire login system. Of course this is just meant to give you the idea of the steps and should by no means be used in a real-world system as is. However you should have a firm understanding of how a basic login system works using PHP/MySQL and a little bit of HTML and CSS. As always if you have any questions/concerns feel free to leave a comment and I’ll get back to you asap.

Cookies and Sessions are extremely useful to a PHP programmer, however they could be considerably confusing to a beginner. Cookies and sessions are used to store pieces of information for a period of time until it is destroyed. This information inside of a cookie or a session can be used to store things like log in information, URL information and much much more.

Cookies

Cookies are pieces of information stored on the client’s machine. The disadvantage here is that cookies can be disabled or ignored from the client’s end. So if you’re using cookies, try not to use them for anything that is crucial to the system functioning(this is what sessions are for… more on that later). The syntax for creating a cookie looks like this…

//A cookie can be equal to a string
$_COOKIE['nameOfCookie'] = 'What information you want to store here';
 
//or a cookie can be equal to a variable
$_COOKIE['nameOfCookie'] = $username;

According to PHP variable declaration rules, you can name the cookie whatever you would like as long as it doesn’t break any of the PHP rules. Data from created cookies can then be used anywhere you like just like any variable such as…

//print the value of the cookie
print($_COOKIE['nameOfCookie']);

Alternately, you can use the isset() method to check to see if a specific cookie has been set. This is more useful when using sessions but we’ll get to that later.

Sessions

Session differ from cookies in that they are stored on the server as opposed to the client. Sessions offer one major advantage over cookies, they cannot be disabled by the user, thus making sessions much more secure than cookies. When dealing with things like log in information and secure data, session are a much better choice than cookies. Sessions are declared using the same conventions as cookies…

//a session can be equal to a string
$_SESSION['nameOfSession'] = 'What information you want to store in the session';
 
//or a session can be equal to a variable
$_SESSION['nameOfSession'] = $username;

This will declare a session variable, however there is one key function that needs to be created prior to using a session variable. The session_start() function needs to be called before any data is sent from the server. Even if a spare white space is sent, the session_start() function will most likely send an error. Whenever you want to use a session variable in a PHP file/function, you must call the session_start() function at the very beginning of the page in order to use a session variable that has been created. This needs to occur even prior to sending the DOCTYPE to the client. To use a session variable the syntax is as follows…

//start the session
session_start();
 
//print the session variable
print($_SESSION['nameOfSession']);

The syntax is similar to using a cookie and alternatively you can use the isset() method to check if a session variable has been created or not. This becomes particularly useful when it comes to creating login systems that keeps users logged in using a session.

In full, you can use sessions or cookies if you like but keep in mind that sessions are stored on the server and cannot be disabled by a user, thus making them much more secure and reliable. In order to create a session, remember to call the session_start() method at the very start of the document or you may not be able to use the session variables.

This is part 3 in a series of JQuery tutorials. I strongly recommend at least reading Part 1 before continuing with this tutorial. Part 2 is optional but would also be a great background before we get started. As for this tutorial, I will be going over creating an executing functions to make your code more efficient.

Often when writing JQuery code(especially for plugins) there are times when you need to execute the same block of code multiple times. Instead of writing them all out individually and making our code really terrible process wise, we can use functions and function calls to call the same block of code over and over.

Creating Functions

You can create a function in 2 different places. The first is in the same script tags, but not inside the document ready function. Or second, you could create a brand new script file and then reference that script file in your header. Inside this script file you could create your method and it would be able to be accessed by the main file.

To create a function, the syntax looks like this…

function nameOfFunction()
{
	//your code here
}

This tells the browser that there is a function called nameOfFunction that is not being passed any parameters. Passing parameters is something I’ll get into a little bit later. Now say you wanted to alert the user with a javascript pop-up box every time this function was run. You could add some code into the function to allow a dialog box to appear like so.

function nameOfFunction()
{
	alert("We are now alerting the user!");
}

Executing Functions

Now that we have a function created, we need to somehow call that function to execute. That’s where our javascript method calls come in. Let’s say we wanted to execute the previous function. The code would look like this.

$(document).ready(function(){
	nameOfFunction();
});

Of course this would call the function immediately after the page was ready. You can use a function call in JQuery in any function. So if you wanted to add it inside of a .click function you could do that as well. That’s all you need to do to execute functions in JQuery.

Passing Arguments to Functions

Let’s say you wanted a function to work with a piece of data from a form, but you didn’t want the function to retrieve that piece of data inside the function. You can use a piece of code called an argument to pass to the function. This allows you to pass values to a function so they can be used. To create a function with an argument then all you need to do is add the argument into the brackets in the function header. It looks like this.

function nameOfFunction(argument)
{
	//your code here
}

Now obviously since we have that argument in the argument ready to do something with it, we may also want to return a value back to the original function so that we can maybe display the result of a calculation or something like that. If we want to return a value all we have to do is insert a return value into our function.

function nameOfFunction(argument)
{
	var total = 10 + argument;
 
	return total;
}

This function will now accept a value, add 10 to that value and return it to the original function call. This way if we need to manipulate some data quite a few times, we could use a function to do that display the result.

Function Calls with Arguments

Now that we have a function made that’s accepting an argument and returning a value, we can use a function call and pass an argument to the function so it can do the calculation and we can then display the result. The function call looks something like this.

$(document).ready(function(){
	alert("The total is = " + nameOfFunction(10);
});

In our JQuery ready function we are now just displaying an alert. Inside the alert we are actually making the function call and passing a value of 10 to our function. The function is then going to add 10 to our passed argument and return a value of 20. The alert therefore is going to display – “The total is = 20″. And that’s all for basic functions and function calls.