IOS开发——Protocol使用协议

@protocol ContactCtrlDelegate 
-(void)DismissContactsCtrl; 
@end 


@interface ContactsCtrl : UIViewController { 
    id <ContactCtrlDelegate> delegate; 
} 
@property (nonatomic, assign) id <ContactCtrlDelegate> delegate; 

@synthesize delegate; 

比如：UITextView 

@protocol UITextViewDelegate <NSObject> 
@optional 
- (BOOL)textViewShouldBeginEditing:(UITextView *)textView; 
- (BOOL)textViewShouldEndEditing:(UITextView *)textView; 
- (void)textViewDidBeginEditing:(UITextView *)textView; 
- (void)textViewDidEndEditing:(UITextView *)textView; 
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text; 
- (void)textViewDidChange:(UITextView *)textView; 
- (void)textViewDidChangeSelection:(UITextView *)textView; 
@end

#import <UIKit/UIKit.h> 

//定义协议 
@protocol ContactCtrlDelegate 
-(void)DismissContactsCtrl; 
@end 

@interface ContactsCtrl : UIViewController { 
    IBOutlet UINavigationBar *ContactNavBar; 
    id <ContactCtrlDelegate> delegate; 
} 
@property (nonatomic, assign) id <ContactCtrlDelegate> delegate; 
-(IBAction)canCelBtn:(id)sender; 
@end 

@implementation ContactsCtrl 
@synthesize delegate; 

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib. 
- (void)viewDidLoad { 
    [super viewDidLoad]; 
    ContactNavBar.topItem.prompt = @"选取联系人发送短信"; 
} 

//调用协议中的方法 
-(IBAction)canCelBtn:(id)sender{ 
    [delegate DismissContactsCtrl]; 
} 

3、ProtocolDemoCtrl.h 

#import <UIKit/UIKit.h> 
#import "ContactsCtrl.h" 
@interface ProtocolDemoCtrl : UIViewController <ContactCtrlDelegate>{//加入托付 
    ContactsCtrl *contactsView; 
} 

4、ProtocolDemoCtrl.m 

#import "ProtocolDemoCtrl.h" 
#define BARBUTTONADD(SELECTOR) [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:SELECTOR] autorelease]; 

@implementation ProtocolDemoCtrl 
@synthesize contactsView; 

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib. 
- (void)viewDidLoad { 
    [super viewDidLoad]; 
    self.navigationItem.rightBarButtonItem = BARBUTTONADD(@selector(addContactAction:)); 
} 

- (void)addContactAction:(id)sender{ 
    ContactsCtrl *contactView = [[ContactsCtrl alloc] initWithNibName:@"ContactsCtrl" bundle:nil]; 
    self.contactsView = contactView; 
    contactsView.delegate = self;//设置托付 
    [self presentModalViewController:contactsView animated:YES]; 
    [contactView release];     
} 

//实现ContactCtrlDelegate协议中的方法 
-(void)DismissContactsCtrl{ 
    [contactsView dismissModalViewControllerAnimated:YES]; 
} 

综上，假设A类.h文件定义了一个协议，在A类里面我们还须要定义一个托付delegate，协议里面有个必须实现的methodA方法（@required，这种方法在实现了协议的类里面实现），在A类的.m文件里须要调用这个methodA方法，我们使用托付调用这个methodA方法

[delegate DismissContactsCtrl]; 

a.delegate = self;//设置托付

假设MethodA返回的是B类的对象，那么在A类中就能够调用B类属性和方法国，B这个类可以调用A的属性和方法。