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Find keys mapped to a value in Swift dictionary
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| 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 | |
| } | |
| } | |
| } |
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