C# enums as function parameters

cenumsfunction-parameterloops

Can you pass a standard c# enum as a parameter?

For example:

enum e1
{
    //...
}

enum e2
{
    //...
}

public void test()
{
    myFunc( e1 );
    myFunc( e2 );
}

public void myFunc( Enum e )
{
    // Iterate through all the values in e
}

By doing this I hope to retrieve all the names within any given enum. What would the Iteration code look like?

Best Answer

This!

        public void Foo(Enum e)
        {
            var names = Enum.GetNames(e.GetType());

            foreach (var name in names)
            {
                // do something!
            }
        }

EDIT: My bad, you did say iterate.

Note: I know I could just do the GetNames() call in my foreach statement, but I prefer to assign that type of thing to a method call first, as it's handy for debugging.

Related Solutions

C++ – How to iterate over an enum

The typical way is as follows:

enum Foo {
  One,
  Two,
  Three,
  Last
};

for ( int fooInt = One; fooInt != Last; fooInt++ )
{
   Foo foo = static_cast<Foo>(fooInt);
   // ...
}

Please note, the enum Last is meant to be skipped by the iteration. Utilizing this "fake" Last enum, you don't have to update your terminating condition in the for loop to the last "real" enum each time you want to add a new enum. If you want to add more enums later, just add them before Last. The loop in this example will still work.

Of course, this breaks down if the enum values are specified:

enum Foo {
  One = 1,
  Two = 9,
  Three = 4,
  Last
};

This illustrates that an enum is not really meant to iterate through. The typical way to deal with an enum is to use it in a switch statement.

switch ( foo )
{
    case One:
        // ..
        break;
    case Two:  // intentional fall-through
    case Three:
        // ..
        break;
    case Four:
        // ..
        break;
     default:
        assert( ! "Invalid Foo enum value" );
        break;
}

If you really want to enumerate, stuff the enum values in a vector and iterate over that. This will properly deal with the specified enum values as well.

Javascript – How to guarantee that the enums definition doesn’t change in JavaScript

Since 1.8.5 it's possible to seal and freeze the object, so define the above as:

const DaysEnum = Object.freeze({"monday":1, "tuesday":2, "wednesday":3, ...})

const DaysEnum = {"monday":1, "tuesday":2, "wednesday":3, ...}
Object.freeze(DaysEnum)

and voila! JS enums.

However, this doesn't prevent you from assigning an undesired value to a variable, which is often the main goal of enums:

let day = DaysEnum.tuesday
day = 298832342 // goes through without any errors

One way to ensure a stronger degree of type safety (with enums or otherwise) is to use a tool like TypeScript or Flow.

Quotes aren't needed but I kept them for consistency.

Best Answer

Related Solutions

C++ – How to iterate over an enum

Javascript – How to guarantee that the enums definition doesn’t change in JavaScript

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