feat: add revertKeyPath() and revertObject() methods to ParseObject

Author: cbaker6

CHANGELOG.md

@@ -4,6 +4,9 @@
 [Full Changelog](https://github.com/parse-community/Parse-Swift/compare/4.9.3...main)
 * _Contributing to this repo? Add info about your change here to be included in the next release_
 
+__New features__
+- Add revertKeyPath() and revertObject() methods to ParseObject which allow developers to revert to original values of key paths or objects after mutating ParseObjects that were already have an objectId  ([#402](https://github.com/parse-community/Parse-Swift/pull/402)), thanks to [Corey Baker](https://github.com/cbaker6).
+
 ### 4.9.3
 [Full Changelog](https://github.com/parse-community/Parse-Swift/compare/4.9.2...4.9.3)
 

Sources/ParseSwift/Objects/ParseObject.swift

@@ -83,6 +83,7 @@ public protocol ParseObject: ParseTypeable,
     /**
      Determines if a `KeyPath` of the current `ParseObject` should be restored
      by comparing it to another `ParseObject`.
+     - parameter key: The `KeyPath` to check.
      - parameter original: The original `ParseObject`.
      - returns: Returns a **true** if the keyPath should be restored  or **false** otherwise.
     */
@@ -140,6 +141,23 @@ public protocol ParseObject: ParseTypeable,
      use `shouldRestoreKey` to compare key modifications between objects.
     */
     func merge(with object: Self) throws -> Self
+
+    /**
+     Reverts the `KeyPath` of the `ParseObject` back to  the original `KeyPath`
+     before mutations began.
+     - throws: An error of type `ParseError`.
+     - important: This reverts to the contents in `originalData`. This means `originalData` should have
+     been populated by calling `mergeable` or some other means.
+    */
+    mutating func revertKeyPath<W>(_ keyPath: WritableKeyPath<Self, W?>) throws where W: Equatable
+
+    /**
+     Reverts the `ParseObject` back to the original object before mutations began.
+     - throws: An error of type `ParseError`.
+     - important: This reverts to the contents in `originalData`. This means `originalData` should have
+     been populated by calling `mergeable` or some other means.
+    */
+    mutating func revertObject() throws
 }
 
 // MARK: Default Implementations
@@ -198,7 +216,7 @@ public extension ParseObject {
         }
         var updated = self
         if shouldRestoreKey(\.ACL,
-                                 original: object) {
+                             original: object) {
             updated.ACL = object.ACL
         }
         return updated
@@ -207,6 +225,45 @@ public extension ParseObject {
     func merge(with object: Self) throws -> Self {
         return try mergeParse(with: object)
     }
+
+    mutating func revertKeyPath<W>(_ keyPath: WritableKeyPath<Self, W?>) throws where W: Equatable {
+        guard let originalData = originalData else {
+            throw ParseError(code: .unknownError,
+                             message: "Missing original data to revert to")
+        }
+        let original = try ParseCoding.jsonDecoder().decode(Self.self,
+                                                            from: originalData)
+        guard hasSameObjectId(as: original) else {
+            throw ParseError(code: .unknownError,
+                             message: "The current object does not have the same objectId as the original")
+        }
+        if shouldRevertKey(keyPath,
+                           original: original) {
+            self[keyPath: keyPath] = original[keyPath: keyPath]
+        }
+    }
+
+    mutating func revertObject() throws {
+        guard let originalData = originalData else {
+            throw ParseError(code: .unknownError,
+                             message: "Missing original data to revert to")
+        }
+        let original = try ParseCoding.jsonDecoder().decode(Self.self,
+                                                            from: originalData)
+        guard hasSameObjectId(as: original) else {
+            throw ParseError(code: .unknownError,
+                             message: "The current object does not have the same objectId as the original")
+        }
+        self = original
+    }
+}
+
+// MARK: Default Implementations (Internal)
+extension ParseObject {
+    func shouldRevertKey<W>(_ key: KeyPath<Self, W?>,
+                            original: Self) -> Bool where W: Equatable {
+        original[keyPath: key] != self[keyPath: key]
+    }
 }
 
 // MARK: Batch Support

Tests/ParseSwiftTests/ParseObjectTests.swift

@@ -427,6 +427,109 @@ class ParseObjectTests: XCTestCase { // swiftlint:disable:this type_body_length
         XCTAssertThrowsError(try score2.merge(with: score))
     }
 
+    func testRevertObject() throws {
+        var score = GameScore(points: 19, name: "fire")
+        score.objectId = "yolo"
+        var mutableScore = score.mergeable
+        mutableScore.points = 50
+        mutableScore.player = "ali"
+        XCTAssertNotEqual(mutableScore, score)
+        try mutableScore.revertObject()
+        XCTAssertEqual(mutableScore, score)
+    }
+
+    func testRevertObjectMissingOriginal() throws {
+        var score = GameScore(points: 19, name: "fire")
+        score.objectId = "yolo"
+        var mutableScore = score
+        mutableScore.points = 50
+        mutableScore.player = "ali"
+        XCTAssertNotEqual(mutableScore, score)
+        do {
+            try mutableScore.revertObject()
+            XCTFail("Should have thrown error")
+        } catch {
+            guard let parseError = error as? ParseError else {
+                XCTFail("Should have casted")
+                return
+            }
+            XCTAssertTrue(parseError.message.contains("Missing original"))
+        }
+    }
+
+    func testRevertObjectDiffObjectId() throws {
+        var score = GameScore(points: 19, name: "fire")
+        score.objectId = "yolo"
+        var mutableScore = score.mergeable
+        mutableScore.points = 50
+        mutableScore.player = "ali"
+        mutableScore.objectId = "nolo"
+        XCTAssertNotEqual(mutableScore, score)
+        do {
+            try mutableScore.revertObject()
+            XCTFail("Should have thrown error")
+        } catch {
+            guard let parseError = error as? ParseError else {
+                XCTFail("Should have casted")
+                return
+            }
+            XCTAssertTrue(parseError.message.contains("objectId as the original"))
+        }
+    }
+
+    func testRevertKeyPath() throws {
+        var score = GameScore(points: 19, name: "fire")
+        score.objectId = "yolo"
+        var mutableScore = score.mergeable
+        mutableScore.points = 50
+        mutableScore.player = "ali"
+        XCTAssertNotEqual(mutableScore, score)
+        try mutableScore.revertKeyPath(\.player)
+        XCTAssertNotEqual(mutableScore, score)
+        XCTAssertEqual(mutableScore.objectId, score.objectId)
+        XCTAssertNotEqual(mutableScore.points, score.points)
+        XCTAssertEqual(mutableScore.player, score.player)
+    }
+
+    func testRevertKeyPathMissingOriginal() throws {
+        var score = GameScore(points: 19, name: "fire")
+        score.objectId = "yolo"
+        var mutableScore = score
+        mutableScore.points = 50
+        mutableScore.player = "ali"
+        XCTAssertNotEqual(mutableScore, score)
+        do {
+            try mutableScore.revertKeyPath(\.player)
+            XCTFail("Should have thrown error")
+        } catch {
+            guard let parseError = error as? ParseError else {
+                XCTFail("Should have casted")
+                return
+            }
+            XCTAssertTrue(parseError.message.contains("Missing original"))
+        }
+    }
+
+    func testRevertKeyPathDiffObjectId() throws {
+        var score = GameScore(points: 19, name: "fire")
+        score.objectId = "yolo"
+        var mutableScore = score.mergeable
+        mutableScore.points = 50
+        mutableScore.player = "ali"
+        mutableScore.objectId = "nolo"
+        XCTAssertNotEqual(mutableScore, score)
+        do {
+            try mutableScore.revertKeyPath(\.player)
+            XCTFail("Should have thrown error")
+        } catch {
+            guard let parseError = error as? ParseError else {
+                XCTFail("Should have casted")
+                return
+            }
+            XCTAssertTrue(parseError.message.contains("objectId as the original"))
+        }
+    }
+
     func testFetchCommand() {
         var score = GameScore(points: 10)
         let className = score.className