Block 使用总结

- (void)testBlockWeakObj1

{

UILabel *tl = [[UILabelalloc]init];//本地局部变量

__weak UILabel *weakTL = tl;//弱引用变量

NSLog(@"%s tl %p",__FUNCTION__ , &tl);

NSLog(@"%s tl %@",__FUNCTION__ , tl);

NSLog(@"%s weakTL %p",__FUNCTION__ , &weakTL);

NSLog(@"%s weakTL %@",__FUNCTION__ , weakTL);

void (^TestBlock)(void) = ^{

//复制tl指针，并且强引用tl

NSLog(@"%s tl %p",__FUNCTION__ , &tl);

NSLog(@"%s tl %@",__FUNCTION__ , tl);

//复制weakTL指针，并且弱引用weakTL

NSLog(@"%s weakTL %p",__FUNCTION__ , &weakTL);

NSLog(@"%s weakTL %@",__FUNCTION__ , weakTL);

};

tl = nil;

TestBlock();

NSLog(@"block is %@", TestBlock);

}

/*输出结果

2014-02-21 17:50:42.591 TestBlock[13888:70b] -[ViewController testBlockWeakObj1] tl 0xbfffc9b0

2014-02-21 17:50:42.591 TestBlock[13888:70b] -[ViewController testBlockWeakObj1] tl <UILabel: 0x8c57c30; frame = (0 0; 0 0); clipsToBounds = YES; userInteractionEnabled = NO; layer = <CALayer: 0x8c562d0>>

2014-02-21 17:50:42.592 TestBlock[13888:70b] -[ViewController testBlockWeakObj1] weakTL 0xbfffc9ac

2014-02-21 17:50:42.592 TestBlock[13888:70b] -[ViewController testBlockWeakObj1] weakTL <UILabel: 0x8c57c30; frame = (0 0; 0 0); clipsToBounds = YES; userInteractionEnabled = NO; layer = <CALayer: 0x8c562d0>>

2014-02-21 17:50:42.592 TestBlock[13888:70b] __35-[ViewController testBlockWeakObj1]_block_invoke tl 0x8b09434

2014-02-21 17:50:42.593 TestBlock[13888:70b] __35-[ViewController testBlockWeakObj1]_block_invoke tl <UILabel: 0x8c57c30; frame = (0 0; 0 0); clipsToBounds = YES; userInteractionEnabled = NO; layer = <CALayer: 0x8c562d0>>

2014-02-21 17:50:42.611 TestBlock[13888:70b] __35-[ViewController testBlockWeakObj1]_block_invoke weakTL 0x8b09438

2014-02-21 17:50:42.612 TestBlock[13888:70b] __35-[ViewController testBlockWeakObj1]_block_invoke weakTL <UILabel: 0x8c57c30; frame = (0 0; 0 0); clipsToBounds = YES; userInteractionEnabled = NO; layer = <CALayer:
0x8c562d0>>

2014-02-21 17:50:42.612 TestBlock[13888:70b] block is <__NSMallocBlock__: 0x8b09420>

*/

- (void)testBlockWeakObj2

{

__block UILabel *tl = [[UILabelalloc]init];//加上block关键字就变成全局变量

__weak UILabel *weakTL = tl;//弱引用变量

NSLog(@"%s tl %p",__FUNCTION__ , &tl);

NSLog(@"%s tl %@",__FUNCTION__ , tl);

NSLog(@"%s weakTL %p",__FUNCTION__ , &weakTL);

NSLog(@"%s weakTL %@",__FUNCTION__ , weakTL);

void (^TestBlock)(void) = ^{

//tl是全局变量，强引用

NSLog(@"%s tl %p",__FUNCTION__ , &tl);

NSLog(@"%s tl %@",__FUNCTION__ , tl);

//复制weakTL指针，并且弱引用weakTL

NSLog(@"%s weakTL %p",__FUNCTION__ , &weakTL);

NSLog(@"%s weakTL %@",__FUNCTION__ , weakTL);

};

tl = nil;

TestBlock();

NSLog(@"block is %@", TestBlock);

}

/*输出结果

2014-02-21 17:55:13.832 TestBlock[13926:70b] -[ViewController testBlockWeakObj1] tl 0xbfffc9b0

2014-02-21 17:55:13.832 TestBlock[13926:70b] -[ViewController testBlockWeakObj1] tl <UILabel: 0x8a32470; frame = (0 0; 0 0); clipsToBounds = YES; userInteractionEnabled = NO; layer = <CALayer: 0x8a37410>>

2014-02-21 17:55:13.832 TestBlock[13926:70b] -[ViewController testBlockWeakObj1] weakTL 0xbfffc994

2014-02-21 17:55:13.833 TestBlock[13926:70b] -[ViewController testBlockWeakObj1] weakTL <UILabel: 0x8a32470; frame = (0 0; 0 0); clipsToBounds = YES; userInteractionEnabled = NO; layer = <CALayer: 0x8a37410>>

2014-02-21 17:55:13.833 TestBlock[13926:70b] __35-[ViewController testBlockWeakObj1]_block_invoke tl 0x8a3bdf8

2014-02-21 17:55:13.833 TestBlock[13926:70b] __35-[ViewController testBlockWeakObj1]_block_invoke tl (null)

2014-02-21 17:55:13.834 TestBlock[13926:70b] __35-[ViewController testBlockWeakObj1]_block_invoke weakTL 0x8a3bdd8

2014-02-21 17:55:13.834 TestBlock[13926:70b] __35-[ViewController testBlockWeakObj1]_block_invoke weakTL (null)

2014-02-21 17:55:13.834 TestBlock[13926:70b] block is <__NSMallocBlock__: 0x8a3bdc0>

*/

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