More map by keyPath

Sources/Guarantee.swift

@@ -105,7 +105,7 @@ public extension Guarantee {
         return rg
     }
 
-    #if swift(>=4)
+    #if swift(>=4) && !swift(>=5.2)
     func map<U>(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ keyPath: KeyPath<T, U>) -> Guarantee<U> {
         let rg = Guarantee<U>(.pending)
         pipe { value in
@@ -117,7 +117,7 @@ public extension Guarantee {
     }
     #endif
 
-	@discardableResult
+    @discardableResult
     func then<U>(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ body: @escaping(T) -> Guarantee<U>) -> Guarantee<U> {
         let rg = Guarantee<U>(.pending)
         pipe { value in
@@ -169,6 +169,21 @@ public extension Guarantee where T: Sequence {
         return map(on: on, flags: flags) { $0.map(transform) }
     }
 
+    #if swift(>=4) && !swift(>=5.2)
+    /**
+     `Guarantee<[T]>` => `KeyPath<T, U>` => `Guarantee<[U]>`
+
+         Guarantee.value([Person(name: "Max"), Person(name: "Roman"), Person(name: "John")])
+            .mapValues(\.name)
+            .done {
+                // $0 => ["Max", "Roman", "John"]
+            }
+     */
+    func mapValues<U>(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ keyPath: KeyPath<T.Iterator.Element, U>) -> Guarantee<[U]> {
+        return map(on: on, flags: flags) { $0.map { $0[keyPath: keyPath] } }
+    }
+    #endif
+
     /**
      `Guarantee<[T]>` => `T` -> `[U]` => `Guarantee<[U]>`
 
@@ -203,6 +218,27 @@ public extension Guarantee where T: Sequence {
         }
     }
 
+    #if swift(>=4) && !swift(>=5.2)
+    /**
+     `Guarantee<[T]>` => `KeyPath<T, U?>` => `Guarantee<[U]>`
+
+         Guarantee.value([Person(name: "Max"), Person(name: "Roman", age: 26), Person(name: "John", age: 23)])
+            .compactMapValues(\.age)
+            .done {
+                // $0 => [26, 23]
+            }
+     */
+    func compactMapValues<U>(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ keyPath: KeyPath<T.Iterator.Element, U?>) -> Guarantee<[U]> {
+        return map(on: on, flags: flags) { foo -> [U] in
+            #if !swift(>=4.1)
+            return foo.flatMap { $0[keyPath: keyPath] }
+            #else
+            return foo.compactMap { $0[keyPath: keyPath] }
+            #endif
+        }
+    }
+    #endif
+
     /**
      `Guarantee<[T]>` => `T` -> `Guarantee<U>` => `Guaranetee<[U]>`
 
@@ -256,6 +292,23 @@ public extension Guarantee where T: Sequence {
         }
     }
 
+    #if swift(>=4) && !swift(>=5.2)
+    /**
+     `Guarantee<[T]>` => `KeyPath<T, Bool>` => `Guarantee<[T]>`
+
+         Guarantee.value([Person(name: "Max"), Person(name: "Roman", age: 26, isStudent: false), Person(name: "John", age: 23, isStudent: true)])
+            .filterValues(\.isStudent)
+            .done {
+                // $0 => [Person(name: "John", age: 23, isStudent: true)]
+            }
+     */
+    func filterValues(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ keyPath: KeyPath<T.Iterator.Element, Bool>) -> Guarantee<[T.Iterator.Element]> {
+        return map(on: on, flags: flags) {
+            $0.filter { $0[keyPath: keyPath] }
+        }
+    }
+    #endif
+
     /**
      `Guarantee<[T]>` => (`T`, `T`) -> Bool => `Guarantee<[T]>`
 

Sources/Thenable.swift

@@ -87,7 +87,7 @@ public extension Thenable {
         return rp
     }
 
-    #if swift(>=4)
+    #if swift(>=4) && !swift(>=5.2)
     /**
      Similar to func `map<U>(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ transform: @escaping(T) throws -> U) -> Promise<U>`, but accepts a key path instead of a closure.
 
@@ -149,6 +149,38 @@ public extension Thenable {
         return rp
     }
 
+    #if swift(>=4) && !swift(>=5.2)
+    /**
+    Similar to func `compactMap<U>(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ transform: @escaping(T) throws -> U?) -> Promise<U>`, but accepts a key path instead of a closure.
+
+    - Parameter on: The queue to which the provided key path for value dispatches.
+    - Parameter keyPath: The key path to the value that is using when this Promise is fulfilled. If the value for `keyPath` is `nil` the resulting promise is rejected with `PMKError.compactMap`.
+    - Returns: A new promise that is fulfilled with the value for the provided key path.
+    */
+    func compactMap<U>(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ keyPath: KeyPath<T, U?>) -> Promise<U> {
+        let rp = Promise<U>(.pending)
+        pipe {
+            switch $0 {
+            case .fulfilled(let value):
+                on.async(flags: flags) {
+                    do {
+                        if let rv = value[keyPath: keyPath] {
+                            rp.box.seal(.fulfilled(rv))
+                        } else {
+                            throw PMKError.compactMap(value, U.self)
+                        }
+                    } catch {
+                        rp.box.seal(.rejected(error))
+                    }
+                }
+            case .rejected(let error):
+                rp.box.seal(.rejected(error))
+            }
+        }
+        return rp
+    }
+    #endif
+
     /**
      The provided closure is executed when this promise is fulfilled.
 
@@ -314,6 +346,21 @@ public extension Thenable where T: Sequence {
         return map(on: on, flags: flags){ try $0.map(transform) }
     }
 
+    #if swift(>=4) && !swift(>=5.2)
+    /**
+     `Promise<[T]>` => `KeyPath<T, U>` => `Promise<[U]>`
+
+         firstly {
+             .value([Person(name: "Max"), Person(name: "Roman"), Person(name: "John")])
+         }.mapValues(\.name).done {
+             // $0 => ["Max", "Roman", "John"]
+         }
+     */
+    func mapValues<U>(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ keyPath: KeyPath<T.Iterator.Element, U>) -> Promise<[U]> {
+        return map(on: on, flags: flags){ $0.map { $0[keyPath: keyPath] } }
+    }
+    #endif
+
     /**
      `Promise<[T]>` => `T` -> `[U]` => `Promise<[U]>`
 
@@ -352,6 +399,27 @@ public extension Thenable where T: Sequence {
         }
     }
 
+    #if swift(>=4) && !swift(>=5.2)
+    /**
+     `Promise<[T]>` => `KeyPath<T, U?>` => `Promise<[U]>`
+
+         firstly {
+             .value([Person(name: "Max"), Person(name: "Roman", age: 26), Person(name: "John", age: 23)])
+         }.compactMapValues(\.age).done {
+             // $0 => [26, 23]
+         }
+     */
+    func compactMapValues<U>(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ keyPath: KeyPath<T.Iterator.Element, U?>) -> Promise<[U]> {
+        return map(on: on, flags: flags) { foo -> [U] in
+          #if !swift(>=4.1)
+            return foo.flatMap { $0[keyPath: keyPath] }
+          #else
+            return foo.compactMap { $0[keyPath: keyPath] }
+          #endif
+        }
+    }
+    #endif
+
     /**
      `Promise<[T]>` => `T` -> `Promise<U>` => `Promise<[U]>`
 
@@ -404,6 +472,23 @@ public extension Thenable where T: Sequence {
             $0.filter(isIncluded)
         }
     }
+
+    #if swift(>=4) && !swift(>=5.2)
+    /**
+     `Promise<[T]>` => `KeyPath<T, Bool>` => `Promise<[T]>`
+
+         firstly {
+             .value([Person(name: "Max"), Person(name: "Roman", age: 26, isStudent: false), Person(name: "John", age: 23, isStudent: true)])
+         }.filterValues(\.isStudent).done {
+             // $0 => [Person(name: "John", age: 23, isStudent: true)]
+         }
+     */
+    func filterValues(on: DispatchQueue? = conf.Q.map, flags: DispatchWorkItemFlags? = nil, _ keyPath: KeyPath<T.Iterator.Element, Bool>) -> Promise<[T.Iterator.Element]> {
+        return map(on: on, flags: flags) {
+            $0.filter { $0[keyPath: keyPath] }
+        }
+    }
+    #endif
 }
 
 public extension Thenable where T: Collection {

Tests/CorePromise/GuaranteeTests.swift

@@ -26,12 +26,12 @@ class GuaranteeTests: XCTestCase {
         wait(for: [ex], timeout: 10)
     }
 
-    #if swift(>=4)
+    #if swift(>=4) && !swift(>=5.2)
     func testMapByKeyPath() {
         let ex = expectation(description: "")
 
-        Guarantee.value("Hello world").map(\.count).done {
-            XCTAssertEqual(11, $0)
+        Guarantee.value(Person(name: "Max")).map(\.name).done {
+            XCTAssertEqual("Max", $0)
             ex.fulfill()
         }
 
@@ -56,6 +56,21 @@ class GuaranteeTests: XCTestCase {
         wait(for: [ex], timeout: 10)
     }
 
+    #if swift(>=4) && !swift(>=5.2)
+    func testMapValuesByKeyPath() {
+        let ex = expectation(description: "")
+
+        Guarantee.value([Person(name: "Max"), Person(name: "Roman"), Person(name: "John")])
+            .mapValues(\.name)
+            .done { values in
+                XCTAssertEqual(["Max", "Roman", "John"], values)
+                ex.fulfill()
+            }
+
+        wait(for: [ex], timeout: 10)
+    }
+    #endif
+
     func testFlatMapValues() {
         let ex = expectation(description: "")
 
@@ -82,6 +97,21 @@ class GuaranteeTests: XCTestCase {
         wait(for: [ex], timeout: 10)
     }
 
+    #if swift(>=4) && !swift(>=5.2)
+    func testCompactMapValuesByKeyPath() {
+        let ex = expectation(description: "")
+
+        Guarantee.value([Person(name: "Max"), Person(name: "Roman", age: 26), Person(name: "John", age: 23)])
+            .compactMapValues(\.age)
+            .done { values in
+                XCTAssertEqual([26, 23], values)
+                ex.fulfill()
+            }
+
+        wait(for: [ex], timeout: 10)
+    }
+    #endif
+
     func testThenMap() {
 
         let ex = expectation(description: "")
@@ -124,6 +154,22 @@ class GuaranteeTests: XCTestCase {
         wait(for: [ex], timeout: 10)
     }
 
+    #if swift(>=4) && !swift(>=5.2)
+    func testFilterValuesByKeyPath() {
+
+        let ex = expectation(description: "")
+
+        Guarantee.value([Person(name: "Max"), Person(name: "Roman", age: 26, isStudent: false), Person(name: "John", age: 23, isStudent: true)])
+            .filterValues(\.isStudent)
+            .done { values in
+                XCTAssertEqual([Person(name: "John", age: 23, isStudent: true)], values)
+                ex.fulfill()
+            }
+
+        wait(for: [ex], timeout: 10)
+    }
+    #endif
+
     func testSorted() {
 
         let ex = expectation(description: "")