指针指向的指针不工作 [英] Pointer to pointer assignment isnt working

问题描述

编辑：我已经修正了 func2（）中的意外参数typo为 MyClass * 不是 MyClass 。

I have fixed the accidental argument typo in func2() to be MyClass* not MyClass.

我有这样的类：

#include "MyClass.h"

class X{
    public:
        X();
        MyClass* m;
        func1();
        func2(MyClass* m, int x);

    private:
}

Source:

#include "X.h"

X::X{
    m = null_ptr;
}

X::func1(){
    //Pass the un-initialized data member m here...
    func2(m, 6);

    //When I get to this point m has not been assigned, even though it was passed as a pointer to func2()
}

X::func2(MyClass* old_obj, int x){
    //Please forgive the memory management for a second....
    MyClass* new_obj = new MyClass(x);

    //This should initialise the data member m??????
    old_obj = new_obj ;
}

但是它不工作 - 我在这里做一个基本的假设？我想这将工作....

However it doesn't work- am I making a fundamental miss-assumption here? I thought this would work....

推荐答案

要修改指针从函数参数，你需要修改原始指针不是复制。

To modify a pointer from function parameter, you need to modify original pointer not it's copy.

 func2(MyClass*& m, int x);
 //            ^

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