使用c ++ std :: unique_ptr<>管理Objective-C对象或std :: shared_ptr<> [英] Managing objective-C objects with c++ std::unique_ptr<> or std::shared_ptr<>
问题描述
Objective-C可以在某种程度上与c ++混合使用，并且可以相互调用.但是，Objective-C对象仍然或多或少是手动管理的，该语言完全没有RAII习惯用法.我想知道是否有可能使用c ++智能指针来管理Objective-C对象的生存期.特别是现在，升压scoped_ptr和shared_ptr都已添加到C ++ 11标准
Objective-C can be mixed with c++ to some extent and can be called to each other. But Objective-C objects still are more or less manually managed, and RAII idiom is entirely absent from the language. I wonder if it is possible to manage the lifetimes of Objective-C objects with c++ smart pointers. Specially now that both boost scoped_ptr and shared_ptr have been added to the C++11 standard
推荐答案
但是，Objective-C对象仍然或多或少是手动管理的，该语言完全没有RAII习惯用法.
But Objective-C objects still are more or less manually managed, and RAII idiom is entirely absent from the language.
我认为这似乎可以回答您的问题.由于Objective-C对象是按引用计数的，因此它们已经满足了创建智能指针的目的:将对象的生命周期与包含对象的方法的范围脱离或联系在一起.可以使用自动释放池重新创建scoped_ptr，和具有-retain--release或strong引用的shared_ptr.
I think this would seem to answer your question anyhow. Because Objective-C objects are reference counted, they already fulfill the purpose smart pointers were created for: to divorce or tie the lifetime of an object from the scope of the method it's contained in. scoped_ptrs can be recreated with autorelease pools, and shared_ptrs with -retain--release or strong references.
但是说不无聊.如果您真的想像这样混合Objective-C和C ++，我们首先需要放松"Objective-C对象"的定义.运行时可以识别以isa作为其第一个成员作为对象的任何东西，我们可以利用这一点并编写一个带有相应对象接口的简单C ++类，以便向其发送消息:
But saying no is boring. If you really want to mingle Objective-C and C++ like this, we'll need to first loosen the definition of "Objective-C object". The runtime recognizes anything with an isa sitting as its first member as an object, and we can take advantage of that and write a simple C++ class with a corresponding object interface so it can be messaged:
@interface CFIObject : NSObject
- (void)doSomething;
@end
struct CFIObject_cxx {
Class isa;
public:
CFIObject_cxx() : isa([CFIObject class]) {}
~CFIObject_cxx() { printf("I'm dying!"); }
};
@implementation CFIObject
- (void)doSomething {
NSLog("I did something.");
}
@end
我们现在可以实例化C ++对象的实例并将其包装在智能指针中，我将有目的地将其分为两种方法以说明对象的寿命:
We can now instantiate an instance of our C++ object and wrap it in a smart pointer, which I'm going to purposefully split into two methods to illustrate the lifetime of the object:
void func() {
// Instantiate a smart pointer with our fake object.
std::unique_ptr<CFIObject_cxx> cppObj (new CFIObject_cxx());
id obj = (__bridge id)(cppObj.get());
// The runtime thinks we're an object.
[obj doSomething];
// aaaand, it's out of scope.
}
int main(int argc, const char **argv) {
func();
return 0;
}
如人们所料，它将打印:
As one would expect, this prints:
2013-12-22 17:23:22.681 Test[77528:303] I did something
I'm dying!
到控制台.
如果需要，可以配备析构函数来调用-dealloc以模拟适当的对象销毁，但是我希望您看到所有这些都是完全不必要的，尤其是当ARC在每个CLANG版本中变得更聪明时.
If need be, the destructor could be outfitted to call through to -dealloc to simulate proper object destruction, but I hope you see that all of this is just wholly unnecessary, especially with ARC getting smarter with each release of CLANG.
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