STD::string 作为动态分配对象的成员参数 [英] STD::string as a Member Parameter for Dynamically Allocated Objects

问题描述

我希望动态分配一组对象(可以是数百个).这些对象的一部分是文本字段.因为 std::string 提供了很好的字符串操作，我更喜欢 std:string 类型的对象成员参数.

I wish to dynamically allocate set of objects(can be several hundreds). Part of those objects are text fields. Because std::string offers nice string manipulations, I would prefer having the object member parameters of type std:string.

然而，std::string 是可动态调整大小的对象.对我来说，这与包含 std::string 的动态分配对象背道而驰:如果 std::string 比计划的要大，则可能存在分配的内存溢出.

However, std::string is dynamically resizable object. To me, this goes against the dynamically allocated objects containing std::string: There could be allocated memory overflow, if the std::string gets larger than planned.

• 请问 std::string 是否适合作为动态分配对象的参数?
• 如何操作std::string，才不会出现内存溢出?
• 即使将动态分配数百个对象，std::string 是否适合作为成员参数?

推荐答案

你的问题有点难以解析，我认为示例代码会让这更容易.我是否正确假设您有一个包含字符串的类，如下所示:

Your question is a little difficult to parse, and sample code would have made that easier, I think. Am I right in assuming that you have a class that contains a string, like so:

class foo {
  public:
    std::string str;
};

你想知道字符串是如何调整大小的?让我试着解释一下:foo 类对象的大小是固定的.字符串成员的大小也是固定的，但它在其实现中包含一个指向额外动态内存(其他地方)的指针，它根据字符串的内容增长或缩小.std::string 的实现会为您解决这个问题，您无需担心.也不会有任何内存溢出 - 例如，字符串的内存是与 foo 对象使用的块不同的内存块.

and you wonder how the string is resized? Let me try and explain: The size of objects of class foo is fixed. The size of the string member is also fixed, but it contains in its implementation a pointer to additional dynamic memory (someplace else) that it is growing or shrinking depending on the contents of the string. The implementation of std::string takes care of this for you, you don't need to worry about it. There won't be any memory overflow either - the string's memory is a different block of memory from the block used by the foo-object, for example.

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