@autoreleasepool在ARC和MRC下的区别

block在ARC和MRC中的声明引用有些区别.

/**

block可以存储在栈中,也可以在堆中

默认存储在栈中,不需要管理内存

存储在堆中的block会对block进行retain操作

*/

//(MRC)block在堆中时,不想对block进行retain操作,前面加__block

//(ARC)前面加__weak或__unsafe_unretained

//__weak和__unsafe_unretained的区别:__weak则在释放时会对对象赋值nil,后者不会

//Block_copy使栈中的block转移到堆中,并对block会引用的对象进行retain操作

//避免block引用的对象进行retain操作,在引用对象声明时前面加__block

1. dog.h (NSObject类)

2. //block用copy来定义,这样block存在于堆中

3. //如果block不是copy到堆中,引用完了对象还在,但block被释放了

[objc] view plain copy print?

#import  

@interface dog : NSObject  

@property (nonatomic, assign) int age;  

@property (nonatomic, copy) void (^myBlock)();  

@end  

2.dog.m

//引用self.age会使retainCount = 2的

//因此以__block typeof(self) mySelf = self;方式重新定义self

2.1 在block nslog中不调用d.age情况下,不需要重新定义self

2.2 在block nslog中调用d.age情况下,需要重新定义self

[objc] view plain copy print?

#import "dog.h"  

@implementation dog  

- (instancetype)init {    

if (self = [super init]) {  

self.age = 10;  

self.myBlock = ^{  

NSLog(@"%d",mySelf.age);  

};  

}  

return self;  

}  

- (void)dealloc {  

NSLog(@"dog - dealloc");  

//对定义时copy的block进行释放  

Block_release(self.myBlock);  

[super dealloc];  

}  

@end  

3.main.m文件

[objc] view plain copy print?

int main(int argc, const charchar * argv[]) {  

//3.1 block在ARC和MRC中的情况  

blockARC_MRC();  

//3.2 copy block情况  

copyBlock();     

return 0;  

}  

3.1 block在ARC和MRC中的情况

/**

block可以存储在栈中,也可以在堆中

默认存储在栈中,不需要管理内存

存储在堆中的block会对block进行retain操作

*/

//(MRC)block在堆中时,不想对block进行retain操作,前面加__block

//(ARC)前面加__weak或__unsafe_unretained

//__weak和__unsafe_unretained的区别:__weak则在释放时会对对象赋值nil,后者不会

//Block_copy使栈中的block转移到堆中,并对block会引用的对象进行retain操作

//避免block引用的对象进行retain操作,在引用对象声明时前面加__block

[objc] view plain copy print?

void blockARC_MRC(){  

__block dog *d = [[dog alloc] init];  

d.age = 12;  

NSLog(@"block引用前:d retainCount = %zd",d.retainCount);  

void (^myBlock)() = ^() {  

NSLog(@"d.age = %d",d.age);  

};  

NSLog(@"block引用后:d retainCount = %zd",d.retainCount);  

Block_copy(myBlock);  

NSLog(@"block copy后:d retainCount = %zd",d.retainCount);  

Block_release(myBlock);  

NSLog(@"block release后:d retainCount = %zd",d.retainCount);  

myBlock();  

NSLog(@"block调用后:d retainCount = %zd",d.retainCount);  

[d release];  

}  

3.2 block中引用成员变量情况

//   1.没有调用d.age时,不需要__block

//   2.调用d.age时.必须要__block

[objc] view plain copy print?

void copyBlock() {  

__block dog *d = [[dog alloc] init];  

d.age = 12;  

NSLog(@"block引用前:d retainCount = %zd",d.retainCount);  

d.myBlock = ^{  

NSLog(@"myBlock -- %d",d.age);  

};  

NSLog(@"block引用后:d retainCount = %zd",d.retainCount);  

d.myBlock();  

NSLog(@"block调用后:d retainCount = %zd",d.retainCount);  

[d release];  

}  

-- end