So if you need a property which might have more than one enum case, you can use OptionSet.
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| struct CakeIngredients: OptionSet { | |
| static let banana = CakeIngredients(rawValue: 1 << 0) | |
| static let strawberry = CakeIngredients(rawValue: 1 << 1) | |
| static let apple = CakeIngredients(rawValue: 1 << 2) | |
| let rawValue: Int | |
| init(rawValue: Int) { | |
| self.rawValue = rawValue | |
| } | |
| } | |
| let cake1: CakeIngredients = [] | |
| let cake2: CakeIngredients = [.banana] | |
| let cake3: CakeIngredients = [.banana, .strawberry] | |
| let cake4: CakeIngredients = [.banana, .strawberry, .apple] |
Bitwise shift operator is used to take advantage of OptionSet features such as intersection and union:
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| print(cake2.intersection(cake3)) //CakeIngredients(rawValue: 1) => banana | |
| print(cake2.union(cake3)) //CakeIngredients(rawValue: 3) => banana, strawberry |
CakeIngredients(rawValue: 3) means banana and strawberry because rawValue of banana is 1 and rawValue of strawberry is 2 and sum is 3.
iOS Tricks 