iOS代理方法和block的使用

创建协议

一.

@protocol SecondViewControllerDelegate <NSObject>

-(void)secondViewControllerDidDit:(NSString *)name;

@end

二.@property(nonatomic,weak)id<SecondViewControllerDelegate> delegate;

三. 

-(void)secondViewControllerDidDit:(NSString *)name{

if ([self.delegaterespondsToSelector:@selector(secondViewControllerDidDit:)]) {

        [self.delegatesecondViewControllerDidDit:@"你好"];

    }

}

四.

遵守协议,设置代理,实现方法

遵守协议

@interface ViewController ()<SecondViewControllerDelegate>

设置代理

second.delegate =self;

实现方法

-(void)secondViewControllerDidDit:(NSString *)name{

    NSLog(@"secondViewControllerDidDit--%@",name);

}

=========================block的使用=========================

1.第二个页面声明block

//<1>声明block

typedef void(^myBlock)(NSString *name);

//<2>声明一个block属性

@property (nonatomic,copy)myBlock block;

 //<3>调用block、传值

    self.block(@"123");

//实现

  NextViewController *next = [[NextViewControlleralloc]init];

    //<4>实现block

    //a:NSString *name   代表传过来的值

    next.block = ^(NSString *name){

        //<5>实现

        NSLog(@"%@",name);

        self.view.backgroundColor = [UIColorcyanColor];

    };