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July 3, 2020 05:16
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替换block原有实现
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#import <Foundation/Foundation.h> | |
typedef struct __block_impl { | |
void *isa; | |
int Flags; | |
int Reserved; | |
void *FuncPtr; | |
}__block_impl; | |
typedef void(^GlobalBlock)(void); | |
void hookFunc() { | |
NSLog(@"hello world"); | |
} | |
void HookBlockToPrintHelloWorld(id blk) { | |
__block_impl *ptr = (__bridge __block_impl *)blk; | |
ptr->FuncPtr = &hookFunc; | |
} | |
int main(int argc, const char * argv[]) { | |
GlobalBlock blk = ^void() { | |
}; | |
HookBlockToPrintHelloWorld(blk); | |
blk(); | |
return 0; | |
} |
原理:参照block内部结构,修改其函数指针即可改变任意block的函数部分
如果想先调用原始实现,再打印 Hello world 呢?
@lexrus 用一个函数指针保存原有的实现,在hookFunc里面调用一下就可以了
膜拜大神!!!
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问题源自:实现下面的函数,将block的实现修改成NSLog(@"hello world"),也就是说,在调完整个函数后调用block()时,并不调用原始实现,而是打“Hello world”
void HookBlockToPrintHelloWorld(id block) {
}