Static Initialization Function in Classes

• Download sample - 0.4 KB

Content

Sometimes when we write a C++ class, we want a static function to be used to initialize the class. For example, a static function is used to initialize a static vector or map. We can do the same thing easily in Java, by Java's static block. How we can do with C++?

At first, let's see how to initialize a normal static member in C++.

class Test1 {
public:
    static string emptyString;
};

string Test1::emptyString = "";
// also can be
// string Test1::emptyString;
// string Test1::emptyString("");

As you saw, we declare a static member variable in the class definition, then define and initialize it in the implementation file (.cpp).

Now we meet the first problem, how to initialize a static collection member? The answer is we must write a static function to do that.

And now we meet the second problem, how to invoke the initialization function? Normally, we will invoke the initialization function in the main function. But I think it's not a good solution because users may forget to invoke the initialization function.

Here is my solution:

class Test2 {
public:
    static vector<string> stringList;
private:
    static bool __init;
    static bool init() {
        stringList.push_back("string1");
        stringList.push_back("string2");
        stringList.push_back("string3");

        return true;
    }
};

// Implement
vector<string> Test2::stringList;
bool Test2::__init = Test2::init();

An additional static member is used in my solution. When the additional static member is initialized, the initialization function is invoked automatically.

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)