How to implement an enum in C++

Question

I am trying to create an enum in C++ and use it in a class. But I am getting the following error:

TestClass.cpp:65:49: error: 'TestNameSpace::TestClass::Buttons' is not a class or namespace:Buttons::Right

I am using Visual Studio 2015. Any assistance would be appreciated.

Here is my code:

TestClass.h:

namespace TestNameSpace
{
    class TestClass
    {
    public:
        enum Buttons { Left, Right, Up, Down, Select, None };
        TestClass();
        ~TestClass();
    private:
        Buttons getButtonType(int buttonValue);
    };
}

TestClass.cpp:

#include "AirController.h"
namespace TestNameSpace
{
    Buttons TestClass::getButtonType(int buttonValue)
    {
        if (buttonValue < 50)   return Buttons::Right;
        if (buttonValue < 195)  return Buttons::Up;
        if (buttonValue < 380)  return Buttons::Down;
        if (buttonValue < 555)  return Buttons::Left;
        if (buttonValue < 790)  return Buttons::Select;
        return Buttons::None;
    }
}

You forgot to #include "TestClass.h" in TestClass.cpp. Also, you need TestClass::Buttons TestClass::getButtonType... because Buttons is inside TestClass. — David Schwartz
– David Schwartz, Commented Dec 1, 2015 at 11:11
Or, alternatively, you could use a trailing return type: auto TestClass::getButtonType(int buttonValue) -> Buttons {... } — user4520
– user4520, Commented Dec 1, 2015 at 11:13
@DavidSchwartz Thanks for the reply mate. I have updated the sample to include the header. I tried prefixing with the class name but it made no difference. — user2109254
– user2109254, Commented Dec 1, 2015 at 11:19

Bartek Banachewicz · Accepted Answer · 2015-12-01 11:12:05Z

3

I got your code to compile by simply adding TestClass:: qualification. That being said, you probably wanted enum class.

You need to #include "TestClass.h" in order to make it visible in that translation unit, when you split it across files.

answered Dec 1, 2015 at 11:12

Bartek Banachewicz

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Comments

leemes · Accepted Answer · 2015-12-01 11:46:03Z

With classical enums, members are accessed without mentioning the name of the enum type. In other words, enum members live in the name space the enum lives in, not inside the enum.

That means, remove Buttons:: in front of the enum values:

TestClass::Buttons TestClass::getButtonType(int buttonValue)
{
    if (buttonValue < 50)   return Right;
    if (buttonValue < 195)  return Up;
    if (buttonValue < 380)  return Down;
    if (buttonValue < 555)  return Left;
    if (buttonValue < 790)  return Select;
    return None;
}

The name of the enum Buttons:: needs to be prefixed when you use the more modern way of declaring enums, that is "scoped enums" or "enum classes":

enum class Buttons { Left, Right, Up, Down, Select, None };

Then, you avoid name clashes with other stuff having the same name like your enum members.

Miguel Mesquita Alfaiate · Accepted Answer · 2015-12-01 11:54:50Z

-1

The enum definition may be placed outside of the class definition, if this is not a design requirement:

enum Buttons { Left, Right, Up, Down, Select, None };

then you access it like this:

Buttons::Left

edited Dec 1, 2015 at 11:54

answered Dec 1, 2015 at 11:11

Miguel Mesquita Alfaiate

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9 Comments

user4520 Over a year ago

And? I think OP knows this. Your edit is false; a standard enum puts all its members in the enclosing namespace, you seem to be talking about enum class.

Bartek Banachewicz Over a year ago

This doesn't answer the question.

Miguel Mesquita Alfaiate Over a year ago

Placing the enum outside of the class definition works, so I think it does answer the question. the OP does not say the enum has to be within the class defintion.

Bartek Banachewicz Over a year ago

No, it doesn't "work", it accomplishes a completely different thing. His code places the enum inside of the class, and that's enough to assume that he wants to have it inside of the class.

Miguel Mesquita Alfaiate Over a year ago

@BartekBanachewicz the OP asks for a solution, and does not pose any restrictions. In my opinion, it is you who is incorrect by making assumptions on what he might or might not want.

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