C++:如何访问名称存储在数组中的成员变量 [英] C++: How to access a member variable whose name is stored in an array

问题描述

假设我有一个这样的字符串数组:

Suppose I have a string array like this:

string registers[2] = {"r0","r1"}

还有这样的结构:

struct cpu {
    int r1;
}

我尝试过这样的事情:

cpu *p = (cpu*)malloc(sizeof(cpu));
cout << p->registers[1] << endl;

但这给出了编译错误.如何实施?

But this gave a compilation error. How to implement this?

问题描述

我需要使用索引访问 cpu 类的成员，所以我想我可以将成员的名称放在数组中，然后使用索引获取成员的名称

I need to access the member of a cpu class using an index so I thought I could just put the names of the memebers in an array and then get the name of the member using the index

推荐答案

您的代码格式完全错误.表达式 p->registers 使用默认运算符 ->，它要求左手运算符是指向类型的指针，该类型的成员的名称用作右-手操作符(寄存器).您的 cpu 不包含 registers.

Your code is completely illformed. Expression p->registers uses default operator -> which requires left-hand operator to be a pointer to a type which would have a member with name used as right-hand operator (registers). Your cpu doesn't contain registers.

无论出于何种原因，模仿您想要的行为的步骤:

Steps to emulate behaviour like one you desire for whatever reason that is:

1. 设计一种方法，通过索引或指向成员的指针将特定的string 与cpu 的成员相关联.
2. 将字符串值映射到索引或指向成员的指针.
3. C++ 允许使用成员运算符来封装它，这将导致类似 p[r0"] 的内容产生对 r0 的引用.

1. design a way to associate particular string to a member of cpu, by index or pointer to member.
2. map the string value to an index or a pointer to member.
3. C++ allows to encapsulate that using member operators,which would result in something like p["r0"] yielding a reference to r0.

在最简单的情况下，当所有元素的类型相同时，您可以只使用 std::map 或类似设计的类，例如

In simplest case, when all elements are of same type, you may just use a std::map or a class designed similarly, e.g.

struct cpu {
    std::map<std::string, int> registers;

    // constructor initializes the map
    cpu() : registers ( { {"r0", 0}, 
                          {"r1", 0} 
                        }) 
    {}
};

这里的表达式 p->registers[r0"] 将提供对与r0"关联的值的引用.钥匙等

Here an expression p->registers["r0"] would give you reference to value associated with "r0" key, etc.

注意 cpu对象的创建应该是

NB The creation of cpu object should be

cpu *p = new cpu();

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