包含字符串键和模板化值的map ... [英] map containing a string key and a templated value...
问题描述
您好，
我正在尝试创建一个地图/字典，其中键的类型已知
即std :: string，但值可以是任何内置类型。即。 int，
double等（地图上的内容<字符串，Twhere T是
模板参数）
To保持值类型我有类似的东西：
模板< class T>
struct数据
{
T值;
}
现在我正在尝试声明如下地图：
std :: map< std :: string，Data> ;;
这不会/不会工作，我不知道怎么声明它？
如果我有一个方法必须将此地图作为参数传递，我将如何使用
？
例如Foo（std :: map< string，Dataparam）不起作用，我不希望
它要么
有人可以请帮助！
Hello,
I am trying to create a map/dictionary where the type of key is known
ie std::string, but the value could be of any built in type. ie. int,
double etc. (something along the lines of map<string, Twhere T is
template argument)
To hold the value type I have something like:
template<class T>
struct Data
{
T value;
}
Now I am trying to declare a map as below:
std::map<std::string, Data>;
this doesn''t/wouldn''t work and I don''t know how to declare it??
if I have a method which has to pass in this map as a parameter, how
would I do it??
e.g Foo(std::map<string, Dataparam ) doesn''t work and I don''t expect
it to either
Can someone please help!
推荐答案
de * ****** @ hotmail.com schrieb：
de*******@hotmail.com schrieb:
您好，
我正在尝试创建一个地图/字典，其中键的类型是已知的
即std :: string，但该值可以是任何内置类型。即。 int，
double等（地图上的内容<字符串，Twhere T是
模板参数）
To保持值类型我有类似的东西：
模板< class T>
struct数据
{
T值;
}
现在我正在尝试声明如下地图：
std :: map< std :: string，Data> ;;
这不行/不行，我不知道怎么声明？
Hello,
I am trying to create a map/dictionary where the type of key is known
ie std::string, but the value could be of any built in type. ie. int,
double etc. (something along the lines of map<string, Twhere T is
template argument)
To hold the value type I have something like:
template<class T>
struct Data
{
T value;
}
Now I am trying to declare a map as below:
std::map<std::string, Data>;
this doesn''t/wouldn''t work and I don''t know how to declare it??
如果你想要一个异构容器，你需要运行时多态性;
你不能单独使用模板。
也就是说，使用一个虚拟基类和模板化的子类，它们实际类型为
。
最简单的方法是使用boost :: any或
boost :: variant<>，它们都做类似的事情：
std： ：map< std :: string，boost :: anymapOfAnyType;
-
Thomas
If you want a heterogenous container, you need run-time polymorphism;
you can''t do it with templates alone.
That is, use a virtual base class and templated sub-classes which hold
the actual type.
The easiest way would be to use either of boost::any or
boost::variant<>, they both do something similar:
std::map<std::string, boost::anymapOfAnyType;
--
Thomas
非常感谢您的及时回复！我可以请问以下
1）会提升::任何让我存储任何类型，包括内置类型和
他们的网站上有很好的例子关于这个特殊的
功能？
2）当你说即使用虚拟基类并模板化
子保持实际类型的类。 - 你的意思是宣布
类似map< string，base *>？是否必须宣布基地
作为模板？
Many Thanks for your prompt reply! Can I please ask following
1) will boost::any let me store any type including built-in types and
are there good examples on their site with regards to this particular
feature?
2) when you said "That is, use a virtual base class and templated
sub-classes which hold the actual type." - did you mean declaring a
something like map<string, base*>? would the base have to be declared
as a template too?
de ******* @ hotmail.com 写道：
你好，
我正在尝试创建一个地图/字典，其中键的类型已知
即std :: string，但值可能是任何内置的在类型。即。 int，
double等（地图上的内容<字符串，Twhere T是
模板参数）
To保持值类型我有类似的东西：
模板< class T>
struct数据
{
T值;
}
现在我正在尝试声明如下地图：
std :: map< std :: string，Data> ;;
这不会/不会工作，我不知道怎么声明它？
如果我有一个方法必须将此地图作为参数传递，我将如何使用
？
例如Foo（std :: map< string，Dataparam）不起作用，我不希望
它要么
有人可以请救命！
Hello,
I am trying to create a map/dictionary where the type of key is known
ie std::string, but the value could be of any built in type. ie. int,
double etc. (something along the lines of map<string, Twhere T is
template argument)
To hold the value type I have something like:
template<class T>
struct Data
{
T value;
}
Now I am trying to declare a map as below:
std::map<std::string, Data>;
this doesn''t/wouldn''t work and I don''t know how to declare it??
if I have a method which has to pass in this map as a parameter, how
would I do it??
e.g Foo(std::map<string, Dataparam ) doesn''t work and I don''t expect
it to either
Can someone please help!
我认为你可以使用
std :: map< std :: string，Data *> ;;
I think you can use
std::map<std::string, Data*>;
这篇关于包含字符串键和模板化值的map ...的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
