Add `.reset()` method to reset given keys back to their default value (#22)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

Defaults.xcodeproj/project.pbxproj

@@ -8,6 +8,7 @@
 
 /* Begin PBXBuildFile section */
 		52D6D9871BEFF229002C0205 /* Defaults.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 52D6D97C1BEFF229002C0205 /* Defaults.framework */; };
+		6614F6E322FC6E1C00B0C9CE /* readme.md in Resources */ = {isa = PBXBuildFile; fileRef = 6614F6E222FC6E1C00B0C9CE /* readme.md */; };
 		8933C7851EB5B820000D00A4 /* Defaults.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8933C7841EB5B820000D00A4 /* Defaults.swift */; };
 		8933C7861EB5B820000D00A4 /* Defaults.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8933C7841EB5B820000D00A4 /* Defaults.swift */; };
 		8933C7871EB5B820000D00A4 /* Defaults.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8933C7841EB5B820000D00A4 /* Defaults.swift */; };
@@ -57,6 +58,7 @@
 		52D6D9E21BEFFF6E002C0205 /* Defaults.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Defaults.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		52D6D9F01BEFFFBE002C0205 /* Defaults.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Defaults.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		52D6DA0F1BF000BD002C0205 /* Defaults.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Defaults.framework; sourceTree = BUILT_PRODUCTS_DIR; };
+		6614F6E222FC6E1C00B0C9CE /* readme.md */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = net.daringfireball.markdown; path = readme.md; sourceTree = "<group>"; };
 		8933C7841EB5B820000D00A4 /* Defaults.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; lineEnding = 0; path = Defaults.swift; sourceTree = "<group>"; usesTabs = 1; };
 		8933C7891EB5B82A000D00A4 /* DefaultsTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; lineEnding = 0; path = DefaultsTests.swift; sourceTree = "<group>"; usesTabs = 1; };
 		AD2FAA261CD0B6D800659CF4 /* Defaults.plist */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.xml; path = Defaults.plist; sourceTree = "<group>"; };
@@ -126,6 +128,7 @@
 		52D6D9721BEFF229002C0205 = {
 			isa = PBXGroup;
 			children = (
+				6614F6E222FC6E1C00B0C9CE /* readme.md */,
 				8933C7811EB5B7E0000D00A4 /* Sources */,
 				8933C7831EB5B7EB000D00A4 /* Tests */,
 				52D6D99C1BEFF38C002C0205 /* Configs */,
@@ -457,6 +460,7 @@
 			isa = PBXResourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				6614F6E322FC6E1C00B0C9CE /* readme.md in Resources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Sources/Defaults/Defaults.swift

@@ -65,6 +65,38 @@ public final class Defaults {
 			suite.removeObject(forKey: key)
 		}
 	}
+	
+	/// Reset keys back to their default values.
+	/// - Parameter keys: Keys to reset.
+	/// - Parameter suite: `UserDefaults` suite.
+	public func reset<T: Codable>(_ keys: Defaults.Key<T>..., suite: UserDefaults = .standard) {
+		reset(keys, suite: suite)
+	}
+	
+	/// Reset an array of keys back to their default values.
+	/// - Parameter keys: Keys to reset.
+	/// - Parameter suite: `UserDefaults` suite.
+	public func reset<T: Codable>(_ keys: [Defaults.Key<T>], suite: UserDefaults = .standard) {
+		for key in keys {
+			key.suite[key] = key.defaultValue
+		}
+	}
+	
+	/// Reset optional keys back to `nil`.
+	/// - Parameter keys: Keys to reset.
+	/// - Parameter suite: `UserDefaults` suite.
+	public func reset<T: Codable>(_ keys: Defaults.OptionalKey<T>..., suite: UserDefaults = .standard) {
+		reset(keys, suite: suite)
+	}
+	
+	/// Reset an array of optional keys back to `nil`.
+	/// - Parameter keys: Keys to reset.
+	/// - Parameter suite: `UserDefaults` suite.
+	public func reset<T: Codable>(_ keys: [Defaults.OptionalKey<T>], suite: UserDefaults = .standard) {
+		for key in keys {
+			key.suite[key] = nil
+		}
+	}
 }
 
 // Has to be `defaults` lowercase until Swift supports static subscripts…

Tests/DefaultsTests/DefaultsTests.swift

@@ -191,4 +191,65 @@ final class DefaultsTests: XCTestCase {
 
 		waitForExpectations(timeout: 10)
 	}
+	
+	func testResetKey() {
+		let defaultString1 = "foo1"
+		let defaultString2 = "foo2"
+		let newString1 = "bar1"
+		let newString2 = "bar2"
+		let key1 = Defaults.Key<String>("key1", default: defaultString1)
+		let key2 = Defaults.Key<String>("key2", default: defaultString2)
+		defaults[key1] = newString1
+		defaults[key2] = newString2
+		defaults.reset(key1)
+		XCTAssertEqual(defaults[key1], defaultString1)
+		XCTAssertEqual(defaults[key2], newString2)
+	}
+	
+	func testResetKeyArray() {
+		let defaultString1 = "foo1"
+		let defaultString2 = "foo2"
+		let defaultString3 = "foo3"
+		let newString1 = "bar1"
+		let newString2 = "bar2"
+		let newString3 = "bar3"
+		let key1 = Defaults.Key<String>("akey1", default: defaultString1)
+		let key2 = Defaults.Key<String>("akey2", default: defaultString2)
+		let key3 = Defaults.Key<String>("akey3", default: defaultString3)
+		defaults[key1] = newString1
+		defaults[key2] = newString2
+		defaults[key3] = newString3
+		defaults.reset(key1, key2)
+		XCTAssertEqual(defaults[key1], defaultString1)
+		XCTAssertEqual(defaults[key2], defaultString2)
+		XCTAssertEqual(defaults[key3], newString3)
+	}
+	
+	func testResetOptionalKey() {
+		let newString1 = "bar1"
+		let newString2 = "bar2"
+		let key1 = Defaults.OptionalKey<String>("optionalKey1")
+		let key2 = Defaults.OptionalKey<String>("optionalKey2")
+		defaults[key1] = newString1
+		defaults[key2] = newString2
+		defaults.reset(key1)
+		XCTAssertEqual(defaults[key1], nil)
+		XCTAssertEqual(defaults[key2], newString2)
+	}
+	
+	func testResetOptionalKeyArray() {
+		let newString1 = "bar1"
+		let newString2 = "bar2"
+		let newString3 = "bar3"
+		let key1 = Defaults.OptionalKey<String>("aoptionalKey1")
+		let key2 = Defaults.OptionalKey<String>("aoptionalKey2")
+		let key3 = Defaults.OptionalKey<String>("aoptionalKey3")
+		defaults[key1] = newString1
+		defaults[key2] = newString2
+		defaults[key3] = newString3
+		defaults.reset(key1, key2)
+		XCTAssertEqual(defaults[key1], nil)
+		XCTAssertEqual(defaults[key2], nil)
+		XCTAssertEqual(defaults[key3], newString3)
+	}
 }

readme.md

@@ -173,6 +173,24 @@ defaults[.isUnicornMode] = true
 
 In contrast to the native `UserDefaults` key observation, here you receive a strongly-typed change object.
 
+### Reset keys to their default values
+
+```swift
+extension Defaults.Keys {
+	static let isUnicornMode = Key<Bool>("isUnicornMode", default: false)
+}
+
+defaults[.isUnicornMode] = true
+//=> true
+
+defaults.reset(.isUnicornMode)
+
+defaults[.isUnicornMode]
+//=> false
+```
+
+This works for `OptionalKey` too, which will be reset back to `nil`.
+
 ### Default values are registered with UserDefaults
 
 When you create a `Defaults.Key`, it automatically registers the `default` value with normal UserDefaults. This means you can make use of the default value in, for example, bindings in Interface Builder.