使用auto作为模板参数 [英] Using auto as a template parameter

问题描述

我试图使用GCC 4.7.1编译下面的 -std = c ++ 11 标志设置：

  std :: map< std :: string，auto> myMap; 
  

我试图创建一个对象来包含大量的各种类型的Json数据字符串，bool）以及子结构（列表，映射），所以我不能在编译时声明字段值的类型，所以我想我会使用 auto

<$ p

$ p> 错误：无效使用'auto'
错误：模板参数2无效
错误：模板参数4无效
错误：无法推断'auto 'from'< expression error>'


是否有特殊的方法使用 auto 作为模板参数，还是不可能？

解决方案

正在寻找的是 boost :: any 。

  std :: map< std :: string，boost :: any> myMap; 
  

auto 可用作动态运行时类型。

I'm attempting to compile the following using GCC 4.7.1 with the -std=c++11 flag set:

std::map<std::string, auto> myMap;

I'm attempting to create an object to contain a large amount of Json data of various types (int string, bool) as well as sub-structures (list, map) so I can't declare the type of the field value at compile time, so I thought I'd use the auto keyword for it.

However, when I try to compile it, I get the following

error: invalid use of ‘auto’
error: template argument 2 is invalid
error: template argument 4 is invalid
error: unable to deduce ‘auto’ from ‘<expression error>’

Is there a special way to use auto as a template argument, or is it just not possible?

解决方案

I think what you are looking for is boost::any.

std::map<std::string, boost::any> myMap;

auto is evaluated during compile time and cannot be used as a dynamic run-time type.

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