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Selector in Objective C
Posted on: November 27, 2009 at 12:00 AM
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In this iPhone selector example, you will learn how to use selector in your iphone app. Though we'll explain it with the help of selector syntax ..But lets first understand what is a selector.

Selector in Objective C

In this iPhone selector example, you will learn how to use selector in your iphone app. Though we'll explain it with the help of selector syntax ..But lets first understand what is a selector.

Selector in Objective C
In short, Selector can either be a name of method or a message to an object when used in the source code. And SEL is the complied form of a Selector. Also remember that all methods with the same name have the same selector. We can also use use selector to invoke a method on object.

In this selector tutorial we are converting the upper case string into the lower case sting using selector.

Let's find out the Iphone selector syntax given below..

selectorAppDelegate.h

#import <UIKit/UIKit.h>

@interface selectorAppDelegate : NSObject <UIApplicationDelegate> {
UIWindow *window;
NSString *string;

}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) NSString *string;

@end

selectorAppDelegate.m

#import "selectorAppDelegate.h"

@implementation selectorAppDelegate

@synthesize window, string;

- (void)applicationDidFinishLaunching:(UIApplication *)application {   

    // Override point for customization after application launch
    [window makeKeyAndVisible];

    NSString *str = @"HELLO, THIS IS NEELAM";
   
    SEL sel = @selector(lowercaseString);
    NSString *lower = (([str respondsToSelector:sel]) ? @"YES" : @"NO");
    NSLog (@"Responds to lowercaseString: %@", lower);
    if ([str respondsToSelector:sel]) //(lower == @"YES")
        NSLog(@"lowercaseString is: %@"  , [str lowercaseString]);
   
}

- (void)dealloc {
    [window release];
    [super dealloc];
}

@end

As you can see in the code, SEL is the complied form of @Selector. A selector can be written as
SEL sel = @selector(lowercaseString);

lowercaseString will change all the uppercase string into the lower case.

On running the application it'll look like as given image..

We have created this cocoa selector tutorial in xcode->Window based application. You just need to copy and paste the code to run the example or you can also Download here.


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Posted on: November 27, 2009

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