When writing enumerations in Objective-C, you can do something like this with the NS_ENUM macro which supports specifying the prefix to be dropped:

typedef NS_ENUM(NSInteger, SomeEnumType) {
    SomeEnumTypeValueOne,
    SomeEnumTypeValueTwo,
    SomeEnumTypeValueThree
};

In Swift, you can access them because they are imported as native Swift enumerations:

var x = SomeEnumType.Two
switch (x) {
case .One:
    NSLog("One")
default:
    NSLog("Something else")
}

But if you have a enumeration already defined in existing Objective-C code like this:

enum SomeEnumType {
    SomeEnumTypeValueOne,
    SomeEnumTypeValueTwo,
    SomeEnumTypeValueThree
};

You can still use them in Swift like this:

var x = SomeEnumTypeValueOne
switch (x.value) {
case SomeEnumTypeValueOne.value:
    NSLog("hello")
default:
    NSLog("hey")
}

On the other hand, if you define an enumeration in Swift and want to be able to use it from Objective-C, use @objc attribute like this:

@objc enum Directions: Int {
    case North
    case South
    case East
    case West
}

which would be the equivalent of this in Objective-C:

typedef NS_ENUM(NSInteger, Directions) {
    DirectionsNorth,
    DirectionsSouth,
    DirectionsEast,
    DirectionsWest
};

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