Here’s a helper method that might come in handy when working with a Swift dictionary. It finds every key mapped to a particular value.
| extension Dictionary where Value: Equatable { | |
| /// Returns all keys mapped to the specified value. | |
| /// “` | |
| /// let dict = ["A": 1, "B": 2, "C": 3] | |
| /// let keys = dict.keysForValue(2) | |
| /// assert(keys == ["B"]) | |
| /// assert(dict["B"] == 2) | |
| /// “` | |
| func keysForValue(value: Value) -> [Key] { | |
| return flatMap { (key: Key, val: Value) -> Key? in | |
| value == val ? key : nil | |
| } | |
| } | |
| } |
This is similar to the allKeysForObject(_:) method of NSDictionary, but it is generic so it can return an array of properly types keys, instead of an array of AnyObject.
