你真的会用block吗？

block作为对象的`属性`
block作为方法的`参数`
block作为`返回值` (扩展性特别强)

在强化一下：

1.block作为对象的属性

Person.h
#import <Foundation/Foundation.h>
@interface Person : NSObject
/* block 在arc下用strong就可以 非ARC下 copy */
/** block */
@property (nonatomic,copy)  void(^block)();
@end

#import "ViewController.h"
#import "Person.h"
@interface ViewController ()
/** Person *p */
@property (nonatomic,strong) Person *p;
@end
- (void)viewDidLoad {
    [super viewDidLoad];
    
    Person *p = [[Person alloc] init];
    void(^XDBlock)() = ^() {
        
        NSLog(@"XDBlock");
    };
    //调用
    // XDBlock();
    p.block = XDBlock;
    _p = p;
    
}
$NSLog：XDBlock

2.block 作为方法的参数

Person.h
#import <Foundation/Foundation.h>

@interface Person : NSObject

- (void)eat:(void(^)(NSString *))block;

@end

Person.m
@implementation Person
- (void)eat:(void (^)(NSString *))block{

    block(@"😄");
}

#import "ViewController.h"
#import "Person.h"
@interface ViewController ()
/** Person *p */
@property (nonatomic,strong) Person *p;
@end
- (void)viewDidLoad {
    [super viewDidLoad];
    
   Person *p = [[Person alloc] init];
    [p eat:^(NSString *a) {
    
        //这里面的代码块就是传递的参数
        NSLog(@"吃东西%@",a);
    }];

    
}
$NSLog：吃东西😄

3.block作为返回值 (扩展性特别强)

Person.h
#import <Foundation/Foundation.h>

@interface Person : NSObject

- (void(^)(int))run;

@end

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

#import "ViewController.h"
#import "Person.h"
@interface ViewController ()
/** Person *p */
@property (nonatomic,strong) Person *p;
@end
- (void)viewDidLoad {
    [super viewDidLoad];
    
   Person *p = [[Person alloc] init];
     Person *p = [[Person alloc] init];
//    [p run:3];
     p.run(3);

    
}
$NSLog：2017-06-13 15:08:32.164 Block[30445:3119801] 跑了3米