Bitwise AND operation on UInt8 enum

Question

Having the following enumeration

enum ColliderType: UInt8 {
    case Hero = 0b1
    case GoblinOrBoss = 0b10
    case Projectile = 0b100
    case Wall = 0b1000
    case Cave = 0b10000
}

I'm trying to do something very simple:

    let combined = ColliderType.Hero.toRaw() | ColliderType.Wall.toRaw()

    // test 'combined' for the 'Wall' bitmask
    if (combined & ColliderType.Wall.toRaw()) { // Compliation error :[

    }

The error I'm getting is as follows

Type 'UInt8' does not conform to protocol 'BooleanType'

the bitwise operator does not return a _boolean_ value for you, but – in your case – an `UInt8` instead, so you may want to compare that number with someone (`>0`) to get a boolean value eventually for the `if` statement. — holex, Oct 29 '14 at 11:43

score 2 · Answer 1 · answered Oct 29 '14 at 11:37

if (combined & ColliderType.Wall.toRaw()) != 0 { // No Compliation error :[

The expression in an if statement must be Boolean. UInt8 isn't a boolean. Pointers are not booleans. Optionals are not booleans. Comparisons give booleans.

This enforces good coding practices; you are forced to write the code that you should have written in C or C++ or Objective-C.

score 2 · Accepted Answer · answered Oct 29 '14 at 11:37

2

It's because combined & ColliderType.Wall.toRaw() returns UInt8 while if is expecting BooleanType.

if (combined & ColliderType.Wall.toRaw()) != 0 {
}

should work.

answered Oct 29 '14 at 11:37

rintaro

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Actually, as of Xcode 6.1, it is `rawValue`, not `toRaw()`. – Martin R Oct 29 '14 at 12:03

Bitwise AND operation on UInt8 enum

2 Answers2