How could I modify the enum so it can have only 2 posible values in a function? C-CodePudding

The following function returns a variable (defined: enum carType { };). How could I modify the enum so it can have only 2 posible values: (3 - Minivan, 4 - Sedan) The function returns the enum value that corresponds to it. Thank you!

typeApp modif_enum(string type) 
{
    return carType;
}

CodePudding user response：

In general the range of enum values is not limited by its enumerators. For example 3 is a valid value of

 enum foo { a,b };

However, the range is limited by the underlying type and since C 11 you can specify that explicitly. For only two possible values you can use bool:

enum class carType : bool { MiniVan = 0, Sedan = 1};
// or just enum class carType : bool { MiniVan,Sedan};

carType modif_enum(const std::string& type) { 
    return static_cast<carType>(type == "Sedan");
}

CodePudding user response：

You can just define the enum values that you want, anything else is not a possible value You might want to include an Invalid state for when the conversion does not work, or return a std::optional, or alternatively throw an exception in that case.

enum class typeApp
{
    Minivan = 3,
    Sedan = 4
};

typeApp modif_enum(string type)
{
    if(type == "Minivan") return typeApp::Minivan;
    if(type == "Sedan") return typeApp::Sedan;

    // maybe return an 'Invalid' value or a std::optional here instead.
    throw std::runtime_error("Invalid enum value");
}