iOS开发Block的介绍以及Block的循环引用问题

#import "ViewController.h"
#import "XMGPerson.h"

@interface ViewController ()
@property (nonatomic, copy) int (^sumBlock)(int, int);
@property (nonatomic, assign) int a;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    
    [self test5];
    /*
     如果【block内部】使用【外部声明的强引用】访问【对象A】, 那么【block内部】会自动产生一个【强引用】指向【对象A】
     如果【block内部】使用【外部声明的弱引用】访问【对象A】, 那么【block内部】会自动产生一个【弱引用】指向【对象A】
     */
}

/**
 *  不可行
 */
- (void)test6
{
    XMGPerson *p = [[XMGPerson alloc] init];
    
    __weak XMGPerson *weakP = p;
    
    p.name = @"Jack";
    
    p.block = ^{ // block1
        XMGPerson *strongP = weakP;
        NSLog(@"block1 -- %@", strongP.name);
        
        dispatch_time_t when = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC));
        dispatch_after(when, dispatch_get_main_queue(), ^{ // block2
            NSLog(@"block2 -- %@", weakP.name);
        });
    };
    
    p.block();
}

/**
 *  可行
 */
- (void)test5
{
    XMGPerson *p = [[XMGPerson alloc] init];
    
    __weak XMGPerson *weakP = p;
    
    p.name = @"Jack";
    
    p.block = ^{ // block1
        NSLog(@"beign-------");
        XMGPerson *strongP = weakP;
        
        dispatch_time_t when = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC));
        dispatch_after(when, dispatch_get_main_queue(), ^{ // block2
            
            // NSLog(@"block2 -- %@", weakP.name);
            NSLog(@"block2 -- %@", strongP.name);
            
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ // block3
                NSLog(@"block3 -- %@", strongP.name);
            });
            
        });
    };
    
    p.block();
}

/**
 *  不可行
 */
- (void)test4
{
    XMGPerson *p = [[XMGPerson alloc] init];
    
    p.name = @"Jack";
    
    p.block = ^{ // block1
        NSLog(@"beign-------");
        
        dispatch_time_t when = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC));
        dispatch_after(when, dispatch_get_main_queue(), ^{ // block2
            NSLog(@"after-----------%@", p.name);
        });
    };
    
    p.block();
}

/**
 *  不可行
 */
- (void)test3
{
    XMGPerson *p = [[XMGPerson alloc] init];
    __weak XMGPerson *weakP = p;
    
    p.name = @"Jack";
    
    p.block = ^{ // block1
        NSLog(@"beign-------");
        XMGPerson *strongP = weakP;
        
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(),
                       ^{ // block2
                           NSLog(@"after-----------%@", strongP.name);
                       });
    };
    
    p.block();
}

/**
 *  可行
 */
- (void)test2
{
    XMGPerson *p = [[XMGPerson alloc] init];
    
    __weak XMGPerson *weakP = p;
    
    p.name = @"Jack";
    p.block = ^{ // block1
        NSLog(@"beign-------");
        
        XMGPerson *strongP = weakP;
        
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(),
                       ^{ // block2
                           NSLog(@"after-----------%@", strongP.name);
                       });
    };
    
    p.block();
}

- (void)test1
{
    XMGPerson *p = [[XMGPerson alloc] init];
    
    __weak XMGPerson *weakP = p;
    
    p.name = @"Jack";
    p.block = ^{
        NSLog(@"-----------%@", weakP.name);
    };
}


#pragma mark - 其他
- (void)test:(int (^)(int, int))sumBlock
{
    
}

- (void)run:(int)a
{
    
}

- (void)testBlock
{
    [self test:^(int a, int b){
        return a + b;
    }];
    
    
    void (^block)() =  ^{
        NSLog(@"-------");
    };
    block();
    
    
    
    
    int (^sumBlock)(int, int) = ^(int num1, int num2){
        return num1 + num2;
    };
    sumBlock(10, 10);
    
    
    int a = 10;
    
    /*
     返回值类型 (^block的变量名)(形参类型列表) = ^(形参列表) {
     // block代码
     };
     block的变量名(实参列表);
     */
}

@end