如何使用一个boost ::互斥作为的std ::地图映射的类型? [英] How to use a boost::mutex as the mapped type in std::map?
问题描述
我想锁定按键/指数另一个地图是这样的:
I would like to lock the keys/index in another map like this:
std::map<int, boost::mutex> pointCloudsMutexes_;
pointCloudsMutexes_[index].lock();
不过,我收到以下错误:
However, I am getting the following error:
/usr/include/c++/4.8/bits/stl_pair.h:113: error: no matching function for call to 'boost::mutex::mutex(const boost::mutex&)'
: first(__a), second(__b) { }
^
这似乎与工作的std ::矢量
,但不能与的std ::地图
。我在做什么错了?
It seems to work with std::vector
, but not with std::map
. What am I doing wrong?
推荐答案
在C ++中,的std ::地图的映射类型
必须是默认构造的和拷贝构造,当调用运算符[]
。然而,的boost ::互斥
明确设计不被拷贝构造,因为它通常是不清楚复制一个互斥体的语义应该是什么。由于的boost ::互斥
不是可复制,使用 pointCloudsMutexes_ [指数]
这样的价值插入编译失败。
In C++ before C++11, the mapped type of a std::map
must be both default-constructible and copy-constructible, when calling operator[]
. However, boost::mutex
is explicitly designed not to be copy-constructible, because it is generally unclear what the semantics of copying a mutex should be. Due to boost::mutex
not being copyable, insertion of such value using pointCloudsMutexes_[index]
fails to compile.
最好的解决方法是使用一些共享的指针的boost ::互斥
作为映射类型,例如:
The best workaround is to use some shared pointer to boost::mutex
as the mapped type, e.g:
#include <boost/smart_ptr/shared_ptr.hpp>
#include <boost/thread/mutex.hpp>
#include <map>
struct MyMutexWrapper {
MyMutexWrapper() : ptr(new boost::mutex()) {}
void lock() { ptr->lock(); }
void unlock() { ptr->unlock(); }
boost::shared_ptr<boost::mutex> ptr;
};
int main() {
int const index = 42;
std::map<int, MyMutexWrapper> pm;
pm[index].lock();
}
PS:C ++ 11移除的映射类型为拷贝构造的要求
PS: C++11 removed the requirement for the mapped type to be copy-constructible.
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