[英]C++ Functions object arguments
How do I have a function that takes in any number of arguments then check its data type accordingly? 我如何有一个函数,该函数接受任意数量的参数,然后相应地检查其数据类型? I understand that in java its Objects..arguments then doing instanceof to check the data type, but in C++? 我知道在Java中它的Objects..arguments然后执行instanceof检查数据类型,但是在C ++中呢?
basically something like converting this into C++ 基本上就像将其转换为C ++
public int Testing(String sql, Object...arguments) throws SQLException{
PreparedStatement ps = con.prepareStatement(sql);
for(int i=0; i< arguments.length; i++){
if (arguments[i] instanceof String)
ps.setString(i+1, arguments[i].toString());
else if (arguments[i] instanceof Integer)
ps.setInt(i+1, Integer.parseInt(arguments[i].toString()));
}
return ps.executeUpdate();
}
While you could use variadic templates or something similar, I'd suggest just using a variant library such as boost::variant
, keeping it simple: 虽然您可以使用可变参数模板或类似的模板,但我建议您仅使用诸如boost::variant
类的变体库,保持简单:
#include <boost/any.hpp>
#include <iostream>
#include <string>
int Testing(std::initializer_list<boost::any> args) {
for(const auto &arg : args) {
std::cout << "Arg type: " << arg.type().name();
if(arg.type() == typeid(int)) { // Check for int
int value = boost::any_cast<int>(arg);
std::cout << " | Int value: " << value << std::endl;
} else if(arg.type() == typeid(std::string)) {
std::string value = boost::any_cast<std::string>(arg);
std::cout << " | String value: " << value << std::endl;
}
// ... same for other types such as float
}
return 0;
}
int main() {
Testing({1, 2});
Testing({std::string("abc"), 1});
return 0;
}
As you see, you can use typeid
to check for the type of the argument and std::initializer_list
to allow arbitrary numbers of arguments. 如您所见,可以使用typeid
来检查参数的类型,并可以使用std::initializer_list
允许任意数量的参数。
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