C ++：如何初始化非整数类型的静态成员变量？

Question

How can I initialize a static object in c++? I'm looking for something like static block in java.

I tried this:

Foo.hpp

class Foo{
    public:
    static Bar b;
    static String s;
    static Bar setB();
};

Foo.cpp

Bar Foo::b = Foo::setB();
String Foo::s = "something";
Bar Foo::setB()
{
    Bar bb;
    bb.use(s);
    return bb;
}

There is no compile error, but it's not working.

Many thanks

Answer 1

Your code:

class Foo{
    public:
    static Bar b;
    static Bar setB();
}

Your comment:

There is no compile error

That is not correct . It can not compile, due to missing semicolon.

When that is pointed out, most SO posters then claim in some comment that "but it's just a typing mistake, I will correct it", thus compounding the error by invalidating already posted answers.

In short, when you post code, do copy and paste the real code . Don't retype it. Copy and paste.

Now, to the core question, the continuation of the above comment, that

it's not working.

Well, assuming that your real code has the appropriate semicolons, and that Bar is defined, etc., then also that part is just plain wrong .

I tested it with Visual C++ and MingW g++, and (when corrected for semicolons etc.) it works just OK.

Answer 2

Bar needs a no-args constructor so that it can initialize itself to the expected value.

No need for Foo::setBar() since Foo will already have the Bar instance.

Answer 3

Your example works, other than the fact that you didn't actually initialize anything:

#include <iostream>

class Foo{
public:
    static int b;
    static int setB();
};

int Foo::b = Foo::setB();
int Foo::setB()
{
    int bb;
    bb = 42;  // Not in your example
    return bb;
}

int main()
{
    std::cout << 42 << std::endl;
}

This prints 42. (Note that I've changed "Bar" to "int" since you didn't post a definition of Bar.)

Answer 4

root cause : no semicolon at the end of the class definition. Works perfectly when I put one.

suggestions: Please give more code(the whole if possible) whenever you ask questions and please don't type the code again instead just copy paste it.