create

Pods/FirebaseFirestore/Firestore/Swift/Source/Codable/ServerTimestamp.swift

@@ -0,0 +1,111 @@
+/*
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#if SWIFT_PACKAGE
+  @_exported import FirebaseFirestoreInternalWrapper
+#else
+  @_exported import FirebaseFirestoreInternal
+#endif // SWIFT_PACKAGE
+
+/// A type that can initialize itself from a Firestore Timestamp, which makes
+/// it suitable for use with the `@ServerTimestamp` property wrapper.
+///
+/// Firestore includes extensions that make `Timestamp` and `Date` conform to
+/// `ServerTimestampWrappable`.
+public protocol ServerTimestampWrappable {
+  /// Creates a new instance by converting from the given `Timestamp`.
+  ///
+  /// - Parameter timestamp: The timestamp from which to convert.
+  static func wrap(_ timestamp: Timestamp) throws -> Self
+
+  /// Converts this value into a Firestore `Timestamp`.
+  ///
+  /// - Returns: A `Timestamp` representation of this value.
+  static func unwrap(_ value: Self) throws -> Timestamp
+}
+
+extension Date: ServerTimestampWrappable {
+  public static func wrap(_ timestamp: Timestamp) throws -> Self {
+    return timestamp.dateValue()
+  }
+
+  public static func unwrap(_ value: Self) throws -> Timestamp {
+    return Timestamp(date: value)
+  }
+}
+
+extension Timestamp: ServerTimestampWrappable {
+  public static func wrap(_ timestamp: Timestamp) throws -> Self {
+    return timestamp as! Self
+  }
+
+  public static func unwrap(_ value: Timestamp) throws -> Timestamp {
+    return value
+  }
+}
+
+/// A property wrapper that marks an `Optional<Timestamp>` field to be
+/// populated with a server timestamp. If a `Codable` object being written
+/// contains a `nil` for an `@ServerTimestamp`-annotated field, it will be
+/// replaced with `FieldValue.serverTimestamp()` as it is sent.
+///
+/// Example:
+/// ```
+/// struct CustomModel {
+///   @ServerTimestamp var ts: Timestamp?
+/// }
+/// ```
+///
+/// Then writing `CustomModel(ts: nil)` will tell server to fill `ts` with
+/// current timestamp.
+@propertyWrapper
+public struct ServerTimestamp<Value>: Codable
+  where Value: ServerTimestampWrappable & Codable {
+  var value: Value?
+
+  public init(wrappedValue value: Value?) {
+    self.value = value
+  }
+
+  public var wrappedValue: Value? {
+    get { value }
+    set { value = newValue }
+  }
+
+  // MARK: Codable
+
+  public init(from decoder: Decoder) throws {
+    let container = try decoder.singleValueContainer()
+    if container.decodeNil() {
+      value = nil
+    } else {
+      value = try Value.wrap(container.decode(Timestamp.self))
+    }
+  }
+
+  public func encode(to encoder: Encoder) throws {
+    var container = encoder.singleValueContainer()
+    if let value = value {
+      try container.encode(Value.unwrap(value))
+    } else {
+      try container.encode(FieldValue.serverTimestamp())
+    }
+  }
+}
+
+extension ServerTimestamp: Equatable where Value: Equatable {}
+
+extension ServerTimestamp: Hashable where Value: Hashable {}