C++类内部结构动态分配的方法

Question

我在分配(::operator new)类中声明的结构(在其方法上)时遇到了一些麻烦，因为它得到了一个不可读的错误：

error: cannot convert 'Automata::state*' to 'state*' in assignment

我试过删除"Automata::“声明，放置"this->”和其他随机的东西，但没有成功。遵循示例代码；

#include <iostream>
#include <new>

class Automata{
    public:
        struct quintuple{
            struct state *stateStr = NULL;
            int stateSize = 0;
        };
        struct state{
            struct symbol *symbolStr = NULL;
        };
        struct symbol{
            char *state = NULL;
            int stateSize = 0;
        };
        struct quintuple quintupleStr;
        //Functions
        void quintuple(int stateValidCounter);
};

void Automata::quintuple(int stateValidCounter){
    this->quintupleStr.stateStr = (struct Automata::state *) ::operator new(sizeof(struct Automata::state) * stateValidCounter);
    return;
}

int main(){
    Automata automata; 
    automata.quintuple(5);
    return 0;
}

/*
g++ -std=c++11 example.cpp -o example.out

example.cpp: In member function 'void Automata::quintuple(int)':
example.cpp:23:30: error: cannot convert 'Automata::state*' to 'state*' in assignment
  this->quintupleStr.stateStr = (struct Automata::state *) ::operator new(sizeof(struct Automata::state) * stateValidCounter);
                              ^
*/

谢谢大家的关注。

Answer 1

老实说，这是一件令人悲伤的劳累事件。如果他接电话的话，我愿意接受他的回答。

答案很简单，就像主部分的@Passer注释一样。

做代码

#include <iostream>
#include <new>

class Automata{
    public:
        struct quintuple{
            struct state *stateStr = NULL;
            int stateSize = 0;
        };
        struct state{....};
        struct quintuple quintupleStr;
        //Functions
        void quintuple(int stateValidCounter);
};

void Automata::quintuple(int stateValidCounter){
    this->quintupleStr.stateStr = (struct Automata::state *) ::operator new(sizeof(struct Automata::state) * stateValidCounter);
    return;
}

int main(){
    Automata automata; 
    automata.quintuple(5);
    return 0;
}

只需切换结构代码位置。

class Automata{
    public:
        struct state{....};
        struct quintuple{
            struct state *stateStr = NULL;
            int stateSize = 0;
        };
        struct quintuple quintupleStr;
        ....;
};

我仍然认为编译器错误有点误导性。