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参考
捕获全局/静态对象类型 <TBC?>
OC代码
int main(int argc, const char * argv[]) {
@autoreleasepool {
NSObject *obj = [[NSObject alloc] init];
NSLog(@"1_obj = %@ - %p", obj, &obj);
void (^block)(void) = ^{
NSLog(@"2_obj = %@ - %p", obj, &obj);
};
NSLog(@"3_obj = %@ - %p", obj, &obj);
block();
NSLog(@"4_obj = %@ - %p", obj, &obj);
}
return 0;
}
MRC 输出:
1_obj = <NSObject: 0x103801d20> - 0x7ffeefbff408
3_obj = <NSObject: 0x103801d20> - 0x7ffeefbff408
2_obj = <NSObject: 0x103801d20> - 0x7ffeefbff3f8 // 捕获了obj瞬时值, 所以是不同的地址, 但也和block一样, 都在栈上
4_obj = <NSObject: 0x103801d20> - 0x7ffeefbff408
ARC 输出:
1_obj = <NSObject: 0x103007670> - 0x7ffeefbff408
3_obj = <NSObject: 0x103007670> - 0x7ffeefbff408
2_obj = <NSObject: 0x103007670> - 0x100503e90 // 指针随block拷贝到堆
4_obj = <NSObject: 0x103007670> - 0x7ffeefbff408
C++代码
MRC/ARC下, 编译的C++代码一致:
int main(int argc, const char * argv[]) {
{ __AtAutoreleasePool __autoreleasepool; /* @autoreleasepool */
NSObject *obj = ((NSObject *(*)(id, SEL))(void *)objc_msgSend)((id)((NSObject *(*)(id, SEL))(void *)objc_msgSend)((id)objc_getClass("NSObject"), sel_registerName("alloc")), sel_registerName("init"));
NSLog((NSString *)&__NSConstantStringImpl__var_folders_p5_mp3284bs2xb073r91w__n99r0000gn_T_main_9da835_mi_0, obj, &obj);
void (*block)(void) = ((void (*)())&__main_block_impl_0((void *)__main_block_func_0, &__main_block_desc_0_DATA, obj, 570425344));
NSLog((NSString *)&__NSConstantStringImpl__var_folders_p5_mp3284bs2xb073r91w__n99r0000gn_T_main_9da835_mi_2, obj, &obj);
((void (*)(__block_impl *))((__block_impl *)block)->FuncPtr)((__block_impl *)block);
NSLog((NSString *)&__NSConstantStringImpl__var_folders_p5_mp3284bs2xb073r91w__n99r0000gn_T_main_9da835_mi_3, obj, &obj);
}
return 0;
}
struct __main_block_impl_0 {
struct __block_impl impl;
struct __main_block_desc_0* Desc;
NSObject *__strong obj; // 捕获
// 第3个入参
__main_block_impl_0(void *fp, struct __main_block_desc_0 *desc, NSObject *__strong _obj, int flags=0) : obj(_obj) {
impl.isa = &_NSConcreteStackBlock;
impl.Flags = flags;
impl.FuncPtr = fp;
Desc = desc;
}
};
static void __main_block_func_0(struct __main_block_impl_0 *__cself) {
// 从block结构中获取捕获的变量
NSObject *__strong obj = __cself->obj; // bound by copy
NSLog((NSString *)&__NSConstantStringImpl__var_folders_p5_mp3284bs2xb073r91w__n99r0000gn_T_main_9da835_mi_1, obj, &obj);
}
// block捕获了对象类型的局部变量, desc 增加了 copy 和 dispose 两个函数 (与对象是否可变无关)★
static struct __main_block_desc_0 {
size_t reserved;
size_t Block_size;
void (*copy)(struct __main_block_impl_0*, struct __main_block_impl_0*);
void (*dispose)(struct __main_block_impl_0*);
} __main_block_desc_0_DATA = { 0, sizeof(struct __main_block_impl_0), __main_block_copy_0, __main_block_dispose_0};
static void __main_block_copy_0(struct __main_block_impl_0*dst, struct __main_block_impl_0*src) {
_Block_object_assign((void*)&dst->obj, (void*)src->obj, 3/*BLOCK_FIELD_IS_OBJECT*/);
}
static void __main_block_dispose_0(struct __main_block_impl_0*src) {
_Block_object_dispose((void*)src->obj, 3/*BLOCK_FIELD_IS_OBJECT*/);
}
捕获对象类型的局部变量, 会增加 copy 和 dispose 函数
