static string constants in class vs namespace for constants [c++](类中的静态字符串常量与常量的命名空间 [c++])
问题描述
I want to declare string constants that will be used across various classes in the project. I am considering two alternatives
Option 1:
#header file
class constants{
static const string const1;
};
#cpp file
const string constants::const1="blah";
Option 2:
#header file
namespace constants{
static const string const1="blah";
};
Just wondering what would be a better implementation.
Already looked at
Where to store Class Specific named constants in C++
Where to put constant strings in C++: static class members or anonymous namespaces
UPDATE:
Option 3:
Based on the suggestions from "potatoswatter" and "sellibitze" i currently have the following implementation?
#header file
namespace constants{
extern const string& const1(); //WORKS WITHOUT THE EXTERN ***WHY***
};
#cpp file
namespace constants{
const string& const1(){static string* str = new string ("blah"); return *str;}
}
I'm including the header file where i need to use the constants. Are there any major cons of this implementation?
Update 2 years later:
Every global accessible by more than one source file should be wrapped in an inline
function so the linker shares the object between the files, and the program initializes it properly.
inline std::string const &const1() {
static std::string ret = "hello, world!";
return ret;
}
The inline
function is implicitly extern
and may be wrapped in a named namespace or a class, if you like. (But don't use a class just to hold static members, as namespaces are better for that. And don't use an anonymous namespace as that would defeat the linker, and each source would see a different std::string
object.)
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