auto from const std :: vector<>&amp ;;对象还是引用？ [英] auto from const std::vector<>&; object or reference?

问题描述

假设我们有一个具有以下接口的对象：

  struct Node_t {
 ... const std： ：vector&东西>& getChilds（）const; 
}节点; 
  

现在，使用 auto 变量如下：

  auto childs = node-> getChilds 
  

childs 的类型是什么？ a std :: vector< c>

childs 将为 std :: vector< something> 。

auto 的功能与模板类型扣除。这里选择的类型与 template< typename T> f（node-> getChilds（））。

b $ b

类似地， auto& 会得到与 template>< typename T& f（T& t）; 和 auto&& 会得到与 template< typename T> f（T& t）; 。

同样适用于所有其他组合，例如 auto const& 或 auto * 。

suppose we have an object with the following interface:

struct Node_t {
 ... const std::vector< something >& getChilds() const;
 } node;

Now, i access the property with an auto variable like this:

auto childs = node->getChilds();

what is the type of childs? a std::vector< something > or a reference to one?

解决方案

The type of childs will be std::vector<something>.

auto is powered by the same rules as template type deduction. The type picked here is the same that would get picked for template <typename T> f(T t); in a call like f(node->getChilds()).

Similarly, auto& would get you the same type that would get picked by template <typename T> f(T& t);, and auto&& would get you the same type that would get picked by template <typename T> f(T&& t);.

The same applies for all other combinations, like auto const& or auto*.

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