學(xué)習(xí)Block的章節(jié)
章節(jié)
Block介紹（源碼解析）
什么是Block
Block的本質(zhì)
代碼被編譯后：
static void _I_MCBlock_method(MCBlock * self, SEL _cmd) {
// int multiplier = 6;
// 此處的變量可以證實(shí)block對(duì)執(zhí)行block函數(shù)的上下文做了數(shù)據(jù)截獲。
int multiplier = 6;
/*
int(^Block)(int) = ^int(int num)
{
return num * multiplier;
};
*/
int(*Block)(int) = ((int (*)(int))&__MCBlock__method_block_impl_0((void *)__MCBlock__method_block_func_0, &__MCBlock__method_block_desc_0_DATA, multiplier));
// Block(2);
((int (*)(__block_impl *, int))((__block_impl *)Block)->FuncPtr)((__block_impl *)Block, 2);
}
__MCBlock__method_block_impl_0 解析：
struct __MCBlock__method_block_impl_0 {
struct __block_impl impl; // 包含isa指針
struct __MCBlock__method_block_desc_0* Desc;
int multiplier;
__MCBlock__method_block_impl_0(void *fp, struct __MCBlock__method_block_desc_0 *desc, int _multiplier, int flags=0) : multiplier(_multiplier) {
impl.isa = &_NSConcreteStackBlock;
impl.Flags = flags;
impl.FuncPtr = fp;
Desc = desc;
}
};
// 由此可見，block確實(shí)可以被認(rèn)為是一個(gè)對(duì)象。
struct __block_impl {
void *isa;
int Flags;
int Reserved;
void *FuncPtr;
};
__MCBlock__method_block_func_0 解析：
// block內(nèi)部函數(shù)
static int __MCBlock__method_block_func_0(struct __MCBlock__method_block_impl_0 *__cself, int num) {
int multiplier = __cself->multiplier; // bound by copy
return num * multiplier;
}
block截獲變量（源碼解析）
觀察哪些類型的變量
OC代碼：
@implementation MCBlock
// 全局變量
int global_var = 4;
// 靜態(tài)全局變量
static int static_global_var = 5;
- (void)method
{
// 基本數(shù)據(jù)類型的局部變量
int var = 1;
// 局部靜態(tài)變量
static int static_var = 2;
// 對(duì)象類型的局部變量
__unsafe_unretained id unsafe_obj = nil;
__strong id strong_obj = nil;
void (^MYBlock)(void) = ^{
NSLog(@"1:%d",global_var);
NSLog(@"2:%d",static_global_var);
NSLog(@"3:%d",var);
NSLog(@"4:%d",static_var);
NSLog(@"5:%@",unsafe_obj);
NSLog(@"6:%@",strong_obj);
};
MYBlock();
}
@end
終端執(zhí)行
clang -rewrite-objc -fobjc-arc MCBlock.m
源碼解析：
// @implementation MCBlock
int global_var = 4;
static int static_global_var = 5;
// 1.先看此處，method的方法實(shí)現(xiàn)變異后：
static void _I_MCBlock_method(MCBlock * self, SEL _cmd) {
int var = 1;
static int static_var = 2;
__attribute__((objc_ownership(none))) id unsafe_obj = __null;
__attribute__((objc_ownership(strong))) id strong_obj = __null;
void (*MYBlock)(void) = ((void (*)())&__MCBlock__method_block_impl_0((void *)__MCBlock__method_block_func_0, &__MCBlock__method_block_desc_0_DATA, var, &static_var, unsafe_obj, strong_obj, 570425344));
((void (*)(__block_impl *))((__block_impl *)MYBlock)->FuncPtr)((__block_impl *)MYBlock);
}
// 2. MYBlock 的本質(zhì)代碼 __MCBlock__method_block_impl_0
struct __MCBlock__method_block_impl_0 {
struct __block_impl impl;
struct __MCBlock__method_block_desc_0* Desc;
// 沒有截取 全局變量 global_var，靜態(tài)全局變量 static_global_var
// block截取了函數(shù)上下文的變量 var（截取值）, *static_var（截取地址）, unsafe_obj（截取對(duì)象包括類型）, strong_obj（截取對(duì)象包括類型）
int var;
int *static_var;
__unsafe_unretained id unsafe_obj;
__strong id strong_obj;
__MCBlock__method_block_impl_0(void *fp, struct __MCBlock__method_block_desc_0 *desc, int _var, int *_static_var, __unsafe_unretained id _unsafe_obj, __strong id _strong_obj, int flags=0) : var(_var), static_var(_static_var), unsafe_obj(_unsafe_obj), strong_obj(_strong_obj) {
impl.isa = &_NSConcreteStackBlock;
impl.Flags = flags;
impl.FuncPtr = fp;
Desc = desc;
}
};
// 3.MYBlock 函數(shù)的內(nèi)部實(shí)現(xiàn)
static void __MCBlock__method_block_func_0(struct __MCBlock__method_block_impl_0 *__cself) {
int var = __cself->var; // bound by copy
int *static_var = __cself->static_var; // bound by copy
__unsafe_unretained id unsafe_obj = __cself->unsafe_obj; // bound by copy
__strong id strong_obj = __cself->strong_obj; // bound by copy
// 全局變量 global_var，靜態(tài)全局變量 static_global_var
NSLog((NSString *)&__NSConstantStringImpl__var_folders_sl_ywy8bht94jx4jvy2k65zlrqc0000gn_T_MCBlock_b5dde7_mi_0,global_var);
NSLog((NSString *)&__NSConstantStringImpl__var_folders_sl_ywy8bht94jx4jvy2k65zlrqc0000gn_T_MCBlock_b5dde7_mi_1,static_global_var);
// var（截取值）, *static_var（截取地址）
NSLog((NSString *)&__NSConstantStringImpl__var_folders_sl_ywy8bht94jx4jvy2k65zlrqc0000gn_T_MCBlock_b5dde7_mi_2,var);
NSLog((NSString *)&__NSConstantStringImpl__var_folders_sl_ywy8bht94jx4jvy2k65zlrqc0000gn_T_MCBlock_b5dde7_mi_3,(*static_var));
// unsafe_obj（截取對(duì)象包括類型）, strong_obj（截取對(duì)象包括類型）
NSLog((NSString *)&__NSConstantStringImpl__var_folders_sl_ywy8bht94jx4jvy2k65zlrqc0000gn_T_MCBlock_b5dde7_mi_4,unsafe_obj);
NSLog((NSString *)&__NSConstantStringImpl__var_folders_sl_ywy8bht94jx4jvy2k65zlrqc0000gn_T_MCBlock_b5dde7_mi_5,strong_obj);
}
// 暫時(shí)不看這些代碼
static void __MCBlock__method_block_copy_0(struct __MCBlock__method_block_impl_0*dst, struct __MCBlock__method_block_impl_0*src) {_Block_object_assign((void*)&dst->unsafe_obj, (void*)src->unsafe_obj, 3/*BLOCK_FIELD_IS_OBJECT*/);_Block_object_assign((void*)&dst->strong_obj, (void*)src->strong_obj, 3/*BLOCK_FIELD_IS_OBJECT*/);}
static void __MCBlock__method_block_dispose_0(struct __MCBlock__method_block_impl_0*src) {_Block_object_dispose((void*)src->unsafe_obj, 3/*BLOCK_FIELD_IS_OBJECT*/);_Block_object_dispose((void*)src->strong_obj, 3/*BLOCK_FIELD_IS_OBJECT*/);}
static struct __MCBlock__method_block_desc_0 {
size_t reserved;
size_t Block_size;
void (*copy)(struct __MCBlock__method_block_impl_0*, struct __MCBlock__method_block_impl_0*);
void (*dispose)(struct __MCBlock__method_block_impl_0*);
} __MCBlock__method_block_desc_0_DATA = { 0, sizeof(struct __MCBlock__method_block_impl_0), __MCBlock__method_block_copy_0, __MCBlock__method_block_dispose_0};
// @end
由此可見：
截獲變量總結(jié)
常見面試題
__block詳解
__block介紹
__block筆試題1-此處是使用
__block筆試題2-此處是賦值
__block本質(zhì)
__block用法1
__block用法2
__block測(cè)試
block 內(nèi)存管理
block的內(nèi)存管理
copy后的指針變化
指針試題-答案是24
面試題
解題
有深度面試題
解題1
解題2
解題3
相關(guān)面試題
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