三种类型
Block有如下三种类型
- NSConcrateGlobalBlock 全局
- NSConcrateStackBlock 栈
- NSConcrateMallocBlock 堆
1. NSConcrateGlobalBlock 位于全局区
当我们声明一个Block,如果这个block没有捕获外部变量，那么这个Block就位于全局区，此时对NSGlobal的retain、copy、release都是无效的，ARC、MRC都是如此
- (void)blockType { void(^block1)(void) = ^{ }; NSLog(@"-- block1 = %@", [block1 class]); }
2021-05-17 17:36:02.791048+0800 MemoryManageDemo[37503:5056528] -- block1 = __NSGlobalBlock__
2. NSConcrateStatckBlock 栈区
block捕获了外部变量，但是没有强引用这个block，直接打印出来
//NSConcrateStackBlock int a = 10; NSLog(@"-- block2 = %@",[^{ NSLog(@"-- a = %@",a); } class]);
2021-05-17 18:35:27.662072+0800 MemoryManageDemo[57159:5148084] -- block2 = __NSStackBlock__
3. NSConcrateMallocBlock 堆区
ARC环境下只有捕获了外部变量，并且有强引用指向该Block(或做为函数返回值)，系统就会自动将NSStackBlock copy到堆上，就是NSConcrateMallocBlock
//NSConcrateMallocBlock int b = 10; void(^block3)(void) = ^{ NSLog(@"-- b = %d", b); }; NSLog(@"-- block3 = %@", [block3 class]);
2021-05-17 18:37:36.525794+0800 MemoryManageDemo[57425:5151753] -- block3 = __NSMallocBlock__
关于Block源码解析的博客:
