How to use custom delegates in Objective-C

You will want to declare a delegate protocol for your class. An example of a delegate protocol and interface for class

Foo

might
look like this:

view plain@class Foo;
@protocol FooDelegate <NSObject>
@optional
- (BOOL)foo:(Foo *)foo willDoSomethingAnimated:(BOOL)flag;
- (void)foo:(Foo *)foo didDoSomethingAnimated:(BOOL)flag;
@end
@interface Foo : NSObject {
NSString *bar;
id <FooDelegate> delegate;
}

@property (nonatomic, retain) NSString *bar;
@property (nonatomic, assign) id <FooDelegate> delegate;

- (void)someAction;

@end

[/code]

Don't forget to synthesize your properties in the

@implementation

.

What this code did was declare a protocol called FooDelegate; a class that conforms to this protocol would be declared like

@interface
SomeClass : SuperClass <FooDelegate> {}

. Because this class conforms to the protocol

FooDelegate

,
it now gets to implement the methods under

FooDelegate

(to
require that these be implemented, use

@required

instead
of

@optional

).
The last step is for a

Foo

object
to be instantiated in the class that conforms to

FooDelegate

,
and for this

Foo

object
to have its delegate property set:

view plainFoo *obj = [[Foo alloc] init];
[obj setDelegate:self];
[/code]

Now, your class is prepared to receive messages from

Foo

objects
that have their delegates set correctly.