How to Initialize a static class object from a static class function

Question

Initializing the static member TestClassObject showing an error LNK2001: unresolved external symbol.

    class TestClass
            {
            public:
                string sClassName;
                string sName;
                string sDescription;


            };

    class TestA
            {

            private:
                static void InitInfo();  
                static TestClass TestClassObject;
            };

    void TestA::InitInfo()
    {
        TestClassObject.sName = "Name";
        TestClassObject.sClassName = "ClassName";
        TestClassObject.sDescription = "Description of class";

    }

Vlad from Moscow · Accepted Answer · 2019-11-19 11:33:26Z

1

You have to define the static data member outside the class definition. Within the class definition it is only declared but not defined.

For example

#include <iostream>
#include <string>

using namespace std;

class TestClass
        {
        public:
            string sClassName;
            string sName;
            string sDescription;


        };

class TestA
        {

        private:
            static TestClass InitInfo();  
            static TestClass TestClassObject;
        };

TestClass TestA::InitInfo()
{
    return { "Name", "ClassName", "Description of class" };
}    

TestClass TestA::TestClassObject = InitInfo();

int main()
{
}

answered Nov 19, 2019 at 11:33

Vlad from Moscow

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9 Comments

Hari Sankar v m Over a year ago

Do i Need to manually Call InitInfo() for initializing the variables. Or only I need to call is the variable TestClassObject?

Aconcagua Over a year ago

@HariSankarvm If you provide a constructor to your class instead of your initInfo function, you could just create the object directly: TestClass TestA::testClassObject("name", "class", "description");

Vlad from Moscow Over a year ago

@HariSankarvm You want to initialize the object by the function. So you should provide a function call to initialize the object.

Aconcagua Over a year ago

@HariSankarvm You could alternatively leave the return type as void and call TestA::initInfo() from within main. That's especially interesting if you want to call it multiple times, as you don't need the assignment any more (but it would then probably better be called reset...).

Vlad from Moscow Over a year ago

@HariSankarvm Without the function you can just write TestClass TestA::TestClassObject = { "Name", "ClassName", "Description of class" };

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