[英]std::vector as a template function argument
I want to make a class method that takes a std::vector reference as an argument and I want to use it with different types of data. 我想创建一个类方法,它将std :: vector引用作为参数,我想将它与不同类型的数据一起使用。
The function should look like: 该函数应如下所示:
void some_function(const std::vector & vect){ //do something with vector }
and I want use it with for example: 我想用它来举例如:
std::vector<int> v1;
some_function(v1);
std::vector<string> v2;
some_function(v2);
I hope that I made my point clear. 我希望我明白我的观点。 Do I have to make a template method like that:
我是否必须制作这样的模板方法:
template<class T>
void some_function(std::vector<T> & vect){}
or can I do it in another way? 或者我可以用另一种方式吗? If I have to, please tell me how I can write that method in a class.
如果必须,请告诉我如何在课堂上编写该方法。
Thanks for help! 感谢帮助!
The right way for a template
function to accept any std::vector
by const&
is: template
函数通过const&
接受任何std::vector
的正确方法是:
template<typename T, typename A>
void some_func( std::vector<T,A> const& vec ) {
}
the second argument is the "allocator", and in some advanced usage of std::vector
it will not be the default one. 第二个参数是“allocator”,在
std::vector
一些高级用法中,它不是默认值。 If you just accept std::vector<T>
, your some_func
will reject std::vector
s with alternative allocators. 如果您只接受
std::vector<T>
,那么some_func
将使用备用分配器拒绝std::vector
。
Now, there are other ways to approach this that I will list quickly. 现在,还有其他方法可以快速列出。 I will list them in decreasing cost:benefit ratio -- the one above is probably what you want, and the next one is sometimes useful, and after that I will branch off into over engineered cases that are rarely worth considering (but might be useful in some corner cases).
我将列出它们降低成本:效益比 - 上面的那个可能是你想要的,下一个有时是有用的,之后我将分支到很少值得考虑的过度工程案例(但可能有用)在一些角落的情况下)。
You could accept an arbitrary type T
by T&&
then test to determine if typename std::remove_reference<T>::type
is a kind of std::vector
. 您可以通过
T&&
接受任意类型T
然后测试以确定typename std::remove_reference<T>::type
是否是一种std::vector
。 This would allow you to do "perfect forwarding" of the incoming std::vector
. 这将允许您对传入的
std::vector
进行“完美转发”。 It would also let you change the predicate you use to test to accept more than just a std::vector
: for the most part, const&
to std::vector
probably just needs some arbitrary random-access container. 它还可以让你改变你用来测试的谓词来接受不仅仅是一个
std::vector
:在大多数情况下, const&
to std::vector
可能只需要一些任意的随机访问容器。
A ridiculously fancy way would be to do a two-step function. 一种荒谬的幻想方式是做两步功能。 The second step takes a type-erased random-access range view (or just a range-view if you don't need random access) for a fixed type
T
with SFINAE to ensure that the incoming object is compatible, the first step deduces the container type of the passed in type and calls the second step in a SFINAE context ( auto some_func(...)->decltype(...)
). 对于具有SFINAE的固定类型
T
,第二步采用类型擦除的随机访问范围视图(或者只是范围视图,如果您不需要随机访问)以确保传入对象兼容,第一步推导出传入类型的容器类型,并调用SFINAE上下文中的第二步( auto some_func(...)->decltype(...)
)。
As type erasure of std::vector<T> const&
to a random-access range view of contiguous T
s doesn't lose much functionality, an advantage would be that you could guarantee that the body of your function is exactly the same for std::vector<T> const&
and for T[n]
and for std::array<T,n>
. 由于
std::vector<T> const&
类型擦除以及连续T
s的随机访问范围视图不会失去太多功能,因此可以保证函数体对于std::vector<T> const&
完全相同std::vector<T> const&
和T[n]
以及std::array<T,n>
。
It isn't a big advantage, especially for the boilerplate required. 这不是一个很大的优势,特别是对于所需的样板。
c++20 may make this much easier, because the multi-step SFINAE above will collapse into a few requires clauses. c ++ 20可以使这更容易,因为上面的多步SFINAE将崩溃成几个require子句。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.