add additional dictionary convenience functions for transformations

MVMCore/MVMCore/Categories/Dictionary+MFConvenience.swift

@@ -192,6 +192,61 @@ public extension Dictionary {
         
         return previousObject
     }
+    
+    /// Transforms dictionary keys without modifying values.
+    /// Deduplicates transformed keys.
+    ///
+    /// Example:
+    /// ```
+    /// ["one": 1, "two": 2, "three": 3, "": 4].mapKeys({ $0.first }, uniquingKeysWith: { max($0, $1) })
+    /// // [Optional("o"): 1, Optional("t"): 3, nil: 4]
+    /// ```
+    ///
+    /// - Parameters:
+    ///   - transform: A closure that accepts each key of the dictionary as
+    ///   its parameter and returns a transformed key of the same or of a different type.
+    ///   - combine:A closure that is called with the values for any duplicate
+    ///   keys that are encountered. The closure returns the desired value for
+    ///   the final dictionary.
+    /// - Returns: A dictionary containing the transformed keys and values of this dictionary.
+    func mapKeys<T>(_ transform: (Key) throws -> T, uniquingKeysWith combine: (Value, Value) throws -> Value) rethrows -> [T: Value] {
+        try .init(map { (try transform($0.key), $0.value) }, uniquingKeysWith: combine)
+    }
+
+    /// Transforms dictionary keys without modifying values.
+    /// Drops (key, value) pairs where the transform results in a nil key.
+    /// Deduplicates transformed keys.
+    ///
+    /// Example:
+    /// ```
+    /// ["one": 1, "two": 2, "three": 3, "": 4].compactMapKeys({ $0.first }, uniquingKeysWith: { max($0, $1) })
+    /// // ["o": 1, "t": 3]
+    /// ```
+    ///
+    /// - Parameters:
+    ///   - transform: A closure that accepts each key of the dictionary as
+    ///   its parameter and returns an optional transformed key of the same or of a different type.
+    ///   - combine: A closure that is called with the values for any duplicate
+    ///   keys that are encountered. The closure returns the desired value for
+    ///   the final dictionary.
+    /// - Returns: A dictionary containing the non-nil transformed keys and values of this dictionary.
+    func compactMapKeys<T>(_ transform: (Key) throws -> T?, uniquingKeysWith combine: (Value, Value) throws -> Value) rethrows -> [T: Value] {
+        try .init(compactMap { (try transform($0.key), $0.value) as? (T, Value) }, uniquingKeysWith: combine)
+    }
+    
+    /// Unconditionally merge another dictionary into this one with preference to the incoming keys.
+    func mergingLeft(_ other: Self) -> Self {
+        return merging(other) { first, second in
+            second
+        }
+    }
+    
+    /// Unconditionally merge this dictionary into another with preference to the existing keys.
+    func mergingRight(_ other: Self) -> Self {
+        return merging(other) { first, second in
+            first
+        }
+    }
 }
 
 public extension Optional where Wrapped == Dictionary<AnyHashable, Any> {