iOS-block三种应用场景

1.把block保存成对象中的属性,在恰当的时刻调用



1.png

2.把block当成方法的参数使用,block的调用在是在方法内部,在外界写block的实现(最常用)



2.png

3.把block当成方法的返回值(比较少用)



3.png

示例1

1.在Person类中

@interface Person : NSObject
@property (nonatomic,strong) void(^myBlock)(int,int);
@end

2.在ViewController类中

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
int a = 12;
int b = 11;
Person *p = [[Person alloc] init];
p.myBlock(a,b);
}

示例2

1.在Person类中

@interface Person : NSObject
- (void)eat:(void(^)())block;
@end

@implementation Person
- (void)eat:(void (^)())block
{
block();
}
@end

2.在ViewController类中

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
// 方式1.先定义,在赋值
//    void(^block)() = ^() {
//        NSLog(@"吃东西");
//    };
//
//    [p eat:block];

// 方式2.直接写block
[p eat:^{
NSLog(@"吃东西");
}];
}

示例3

1.在Person类中

@interface Person : NSObject
- (void(^)(int))run;
@end

@implementation Person
- (void (^)(int))run
{
return ^(int b){
NSLog(@"跑了--%d米",b);
};
}
@end

2.在ViewController类中

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
p.run(5);
}