How to use `typedef NS_ENUM` to return `float` values?

Question

In the code (below) LINE_WIDTH is declared a typedef for enumeration where the names Large, Medium, Small and Hairline are int co

Answer 1

In Swift you can use type double for enums

enum Constants: Double {
    case π = 3.14159
    case e = 2.71828
    case φ = 1.61803398874
    case λ = 1.30357
}

To know much about practical usage of enums in swift please refer https://appventure.me/2015/10/17/advanced-practical-enum-examples/

Answer 2

Objective-C doesn't support non-integer enum values. Your only option is to provide code that converts the enum value to a float value.

One option is to create a simple function such as:

float LINE_WIDTH_float(LINE_WIDTH width);

Put that in the same .h as the enum declaration. Then add the following to some appropriate .m or .c file:

float LINE_WIDTH_float(LINE_WIDTH width) {
    switch (width) {
        case LINE_WIDTH_Large:
            return 1.5f;
        case LINE_WIDTH_Medium:
            return 1.0f;
        case LINE_WIDTH_Small:
            return 0.5f;
        case LINE_WIDTH_Hairline:
            return 0.25f;
        default:
            return 0.0f;
    }
}

So somewhere you have an enum value:

LINE_WIDTH someWidth = LINE_WIDTH_Medium;
float width = LINE_WIDTH_float(someWidth);

Another option would be to define an array of float.

In the same .h as the enum add:

extern float *LINE_WIDTH_float;

Then in some appropriate .m or .c, you can add:

float *LINE_WIDTH_float = { 1.5, 1.0, 0.5, 0.25 };

Then to use this you can do:

LINE_WIDTH someWidth = LINE_WIDTH_Medium;
float width = LINE_WIDTH_float[someWidth];

Note that this is less safe than the first approach. It will likely crash if your enum value is set to something other than a valid enum value or if you add a new enum value but forget to update the values in the array.