如何在Visual Studio中初始化C ++类中的静态const浮点数

Question

I have a code like this:

class MyClass
{
   private:
     static const int intvalue= 50;
     static const float floatvalue = 0.07f;
 };

in Visual studio 2010 and I am getting this error:

Myclasses.h(86): error C2864: 'MyClass::floatvalue : only static const integral data members can be initialized within a class

So how to initialize a static constant float in c++?

If I use constructor, every time that an object of this class is created, the variable is initialized which is not good.

apparently the code is compiled with GCC on Linux.

Answer 1

MyClass.h

class MyClass
{
   private:
     static const int intvalue = 50; // can provide a value here (integral constant)
     static const float floatvalue; // canNOT provide a value here (not integral)
};

MyClass.cpp

const int MyClass::intvalue; // no value (already provided in header)
const float MyClass::floatvalue = 0.07f; // value provided HERE

---

Also, concerning

apparently the code is compiled with GCC on Linux.

This is due to an extension. Try with flags like -std=c++98 (or -std=c++03 , or -std=c++11 if your version is recent enough) and -pedantic and you will (correctly) get an error.

Answer 2

Try the following.

In the header file, instead of your current statement write:

static const float floatvalue;

In the CPP file, write:

const float MyClass::floatvalue = 0.07f;

Answer 3

You have to define them outside of the class, as follows:

const int MyClass::intvalue = 50;
const float MyClass::floatvalue = 0.07f;

Of course, this shouldn't be done in a header, or you will get a multiple instance error. With int s, you can fake them using enum {intvalue = 50}; , that won't work with floats, though.