使用Objective-C的method_invoke在ARC下调用void方法 [英] Using Objective-C's method_invoke to call a void method under ARC

问题描述

在iOS上，我尝试从Objective-C运行时使用method_invoke函数(

On iOS, I'm attempting to use the method_invoke function from the Objective-C runtime (reference) in order to call an Objective-C method that is declared with a return type of void.

这在非ARC代码中可以正常工作，但是在启用ARC的情况下，调用objc_retain中的方法后会崩溃.我认为这是发生了什么事，就是编译器注意到了method_invoke的返回类型id，并试图保留method_invoke返回的值(请注意，method_invoke旨在返回其返回值).调用.)

This works fine in non-ARC code, but with ARC enabled, I get a crash after the invocation of the method in objc_retain. I think what's going on is that the compiler notices method_invoke's return type of id, and attempts to retain the value returned by method_invoke (note that method_invoke is meant to return the return value of the method it invokes).

让编译器知道在这种特定情况下，method_invoke的返回值是垃圾且不应保留的正确方法是什么?以下内容似乎可行，但从概念上讲似乎是错误的:

What's the correct way to let the compiler know that in this specific case, the return value of method_invoke is garbage and should not be retained? The following appears to work, but seems conceptually wrong:

(void)((__bridge void *)method_invoke(target, method));

(void)((__bridge void *)method_invoke(target, method));

这似乎不起作用(在objc_retain中仍然崩溃:

This does not seem to work (still crashes in objc_retain:

(void)method_invoke(target, method)

(void)method_invoke(target, method)

这里是否有更正确的方法?

Is there a more correct approach here?

推荐答案

This question actually gave me the idea for a better solution.

基本方法是创建引用具有正确签名(无效返回类型)的method_invoke的函数指针，并将method_invoke强制转换为该函数指针，然后通过该函数指针进行调用.

The basic approach was to create a function pointer referencing method_invoke with the correct signature (void return type) and cast method_invoke into this function pointer, and then call through the function pointer.

因此，大致而言:

static void (*_method_invoke_void)(id, Method, ...) = (void (*)(id, Method, ...)) method_invoke;
... snip ...
_method_invoke_void(target, method);

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