问题描述
我来自node.js,我想知道在C ++中是否有办法做到这一点.与C ++等效的是什么
I'm coming from node.js and I was wondering if there is a way to do this in C++. What would be the C++ equivalent of:
var string = "hello";
string = return_int(string); //function returns an integer
// at this point the variable string is an integer
所以在C ++中,我想做这样的事情...
So in C++ I want to do something kind of like this...
int return_int(std::string string){
//do stuff here
return 7; //return some int
}
int main(){
std::string string{"hello"};
string = return_int(string); //an easy and performant way to make this happen?
}
我正在使用JSON,我需要枚举一些字符串.我确实意识到我可以将 return_int()
的返回值分配给另一个变量,但是我想知道是否有可能将变量的类型从字符串重新分配给int以进行学习和可读性.
I'm working with JSON and I need to enumerate some strings. I do realize that I could just assign the return value of return_int()
to another variable, but I want to know if it's possible to reassign the type of variable from a string to an int for sake of learning and readability.
推荐答案
C ++语言本身没有任何允许这样做的东西.变量不能更改其类型.但是,您可以使用允许其数据动态更改类型的包装器类,例如 boost :: any
或 boost :: variant
(C ++ 17添加了 std :: any
和 std :: variant
):
There is nothing in the C++ language itself that allows this. Variables can't change their type. However, you can use a wrapper class that allows its data to change type dynamically, such as boost::any
or boost::variant
(C++17 adds std::any
and std::variant
):
#include <boost/any.hpp>
int main(){
boost::any s = std::string("hello");
// s now holds a string
s = return_int(boost::any_cast<std::string>(s));
// s now holds an int
}
#include <boost/variant.hpp>
#include <boost/variant/get.hpp>
int main(){
boost::variant<int, std::string> s("hello");
// s now holds a string
s = return_int(boost::get<std::string>(s));
// s now holds an int
}
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