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Ethan Lim
Ethan Lim

Reputation: 159

C++ enum in class member functions

For enums within a class...

Incorrect :

class MyClass{
             public:
               enum kHTTPMethods {GET,PUT,POST}
};

void MyClass::Func(){
    kHTTPMethods method = kHTTPMethod.GET;
}

1) Am I right to say this does not work because . operator can only be use on objects (instances) of a class?

Correct:

void MyClass::Func(){
    kHTTPMethods method = GET; 
}

2) Am I right to say this is correct because all the elements of the class becomes globally scoped within the class?

Upvotes: 3

Views: 4707

Answers (2)

Tony Delroy
Tony Delroy

Reputation: 106246

Well, for your first question the issue is that the enumerations are put in the scope of class MyClass. Anyway, whether or not you have an object, . wouldn't let you refer to the enumerations, you need :: to refer to things in a specific scope. The following will compile, but the corrected MyClass:: scope isn't necessary or useful (i.e. you can just say method = GET because func is in the same scope as GET).

class MyClass
{
  public:
    enum kHTTPMethods {GET,PUT,POST};
    void func() {
        kHTTPMethods method = MyClass::GET;
    }
};

C++11 added an enum class that puts them in their own nested scope (such that you must prefix them with [...::MyClass:: ] kHTTPMethods:: everywhere), but you have to change your code to use that:

class MyClass
{
  public:
    enum class kHTTPMethods {GET,PUT,POST};    // note "class" after "enum"
    void func() {
        kHTTPMethods method = kHTTPMethods::GET;
    }
};

For your second question, yeah - that's about the size of it, though I'd phrase it as I have above.

Upvotes: 7

Peng Zhang
Peng Zhang

Reputation: 3595

For your 1st question, YES. As far as I know, the . operator is only used on object to access member variables and member methods.

For your 2nd question. YES.

Everything within the brackets of MyClass::Func(){} has class scope, because of the MyClass:: preceding Func(). Meanwhile, GET has class scope too. Thus, you can refer to GET directly.

Upvotes: 1

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