C ++中的异构容器 [英] Heterogeneous containers in C++
问题描述
我看到这个漂亮的图形,它根据不同的数据需求分类哪个STL容器,如:
I saw this nice graphic which classifies which STL container would suit based on different requirements of data such as:
- 固定大小Vs变量大小
-- Fixed Size Vs Variable size
- 相同类型的数据与不同类型的数据
-- Data of same tyme Vs different type
- 排序与未排序的数据
-- Sorted Vs unsorted data
- 顺序与随机存取
-- Sequential Vs random access
http:/ /plasmahh.projectiwear.org/cce_clean.svg
我注意到那张图片,C ++ STL没有容器
I notice in that image, that C++ STL there is no container which is
- 变量大小
- 异质(不同类型的数据)。
不是C ++有这样的东西吗?
Doesn't C++ have something for this?
推荐答案
很好的一般情况下, C ++容器设计为使用模板保存单个类型的对象。如果你想要不同类型的所有派生自一个类型,你可以存储一个指针的容器(我想你也可以有一个容器void *任何东西...)。 std :: vector< MyBaseType *>。
Well generally C++ Containers are designed to hold objects of a single type using templates. If you want different types that are all derived from one type you can store a container of pointers (I guess you could also have a container of void* to anything...) e.g. std::vector<MyBaseType*>.
如果你想要完全不相关的类型,你可以存储可以安全地引用其他类型的对象,例如boost :: any 。
If you want completely unrelated types, you can store objects that can safely reference those other types, such as boost::any.
http:// www.boost.org/doc/libs/1_47_0/doc/html/any.html
关于boost网站的一些示例:
Some examples off the boost site:
#include <list>
#include <boost/any.hpp>
using boost::any_cast;
typedef std::list<boost::any> many;
void append_int(many & values, int value)
{
boost::any to_append = value;
values.push_back(to_append);
}
void append_string(many & values, const std::string & value)
{
values.push_back(value);
}
bool is_int(const boost::any & operand)
{
return operand.type() == typeid(int);
}
bool is_char_ptr(const boost::any & operand)
{
try
{
any_cast<const char *>(operand);
return true;
}
catch(const boost::bad_any_cast &)
{
return false;
}
}
boost :: variant类似,允许的类型,而不允许您容器中的任何类型。
boost::variant is similar, but you specify all the allowed types, rather than allowing any type in your container.
http://www.boost.org/doc/libs/1_47_0/doc/html/variant.html
std::vector< boost::variant<unsigned, std::string> > vec;
vec.push_back( 44);
vec.push_back( "str" );
vec.push_back( SomthingElse(55, 65) ); //not allowed
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