将具有非可复制字段的对象插入std :: vector中 [英] Inserting an object having a non copyable field into an std::vector

问题描述

我知道以下代码不会编译，因为A的move构造函数被删除，因为互斥不可移动。

I understand that the following code does not compile since the move constructor of A is deleted because the mutex is not movable.

class A {
  public:
    A(int i) {}

  private:
    std::mutex m;

};


int main() {    
    std::vector<A> v;
    v.emplace_back(2);
}

但如果我想要 A 要存储在std容器中我应该怎么走这个？我很好与 A 正在构建内部的容器。

But if I want my A to be stored in an std container how should I go about this? I am fine with A being constructed "inside" the container.

推荐答案

std :: vector :: emplace_back 矢量的能力。由于向量的所有元素都是连续的，这意味着将所有现有元素移动到新分配的存储。因此，实现 emplace_back 的代码通常需要调用move构造函数（即使对于一个空向量，它将被称为零次）。

std::vector::emplace_back may need to grow a vector's capacity. Since all elements of a vector are contiguous, this means moving all existing elements to the new allocated storage. So the code implementing emplace_back needs to call the move constructor in general (even though for your case with an empty vector it would call it zero times).

如果你使用 std :: list< A> ，你不会得到这个错误。

You wouldn't get this error if you used, say, std::list<A>.

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