Add build infrastructure for Codable support in Firestore (#815)

* Add Firestore_SwiftTests_iOS target to Xcode

* Add FirebaseFirestoreSwift podspec

* Add Firestore_SwiftTests_iOS to the Podfile

* Add CodableGeoPoint and tests

* Version FirebaseFirestoreSwift separately

1 files changed, 62 insertions, 0 deletions

diff --git a/Firestore/Swift/Source/Codable/CodableGeoPoint.swift b/Firestore/Swift/Source/Codable/CodableGeoPoint.swift
new file mode 100644
index 0000000..fa56340
--- /dev/null
+++ b/Firestore/Swift/Source/Codable/CodableGeoPoint.swift
@@ -0,0 +1,62 @@
+/*
+ * Copyright 2018 Google
+ *
+ * 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.
+ */
+
+import FirebaseFirestore
+
+/**
+ * A protocol describing the encodable properties of a GeoPoint.
+ *
+ * Note: this protocol exists as a workaround for the Swift compiler: if the GeoPoint class was
+ * extended directly to conform to Codable, the methods implementing the protcol would be need to be
+ * marked required but that can't be done in an extension. Declaring the extension on the protocol
+ * sidesteps this issue.
+ */
+fileprivate protocol CodableGeoPoint: Codable {
+  var latitude: Double { get }
+  var longitude: Double { get }
+
+  init(latitude: Double, longitude: Double)
+}
+
+/** The keys in a GeoPoint. Must match the properties of CodableGeoPoint. */
+fileprivate enum GeoPointKeys: String, CodingKey {
+  case latitude
+  case longitude
+}
+
+/**
+ * An extension of GeoPoint that implements the behavior of the Codable protocol.
+ *
+ * Note: this is implemented manually here because the Swift compiler can't synthesize these methods
+ * when declaring an extension to conform to Codable.
+ */
+extension CodableGeoPoint {
+  public init(from decoder: Decoder) throws {
+    let container = try decoder.container(keyedBy: GeoPointKeys.self)
+    let latitude = try container.decode(Double.self, forKey: .latitude)
+    let longitude = try container.decode(Double.self, forKey: .longitude)
+    self.init(latitude: latitude, longitude: longitude)
+  }
+
+  public func encode(to encoder: Encoder) throws {
+    var container = encoder.container(keyedBy: GeoPointKeys.self)
+    try container.encode(latitude, forKey: .latitude)
+    try container.encode(longitude, forKey: .longitude)
+  }
+}
+
+/** Extends GeoPoint to conform to Codable. */
+extension GeoPoint: CodableGeoPoint {}