Add code docs

Sources/ComposableKeychain/Interface.swift

@@ -1,22 +1,22 @@
 import Foundation
 
 public struct KeychainClient {
-  public var getString: (_ key: String) throws -> String?
-  public var getData: (_ key: String) throws -> Data?
-  public var setString: (_ value: String, _ key: String) throws -> Void
-  public var setData: (_ value: Data, _ key: String) throws -> Void
-  public var remove: (_ key: String) throws -> Void
+  public var getString: (_ key: Key) throws -> String?
+  public var getData: (_ key: Key) throws -> Data?
+  public var setString: (_ value: String, _ key: Key) throws -> Void
+  public var setData: (_ value: Data, _ key: Key) throws -> Void
+  public var remove: (_ key: Key) throws -> Void
   public var removeAll: () throws -> Void
-  public var contains: (_ key: String) throws -> Bool
+  public var contains: (_ key: Key) throws -> Bool
 
   public init(
-    getString: @escaping (_ key: String) throws -> String?,
-    getData: @escaping (_ key: String) throws -> Data?,
-    setString: @escaping (_ value: String, _ key: String) throws -> Void,
-    setData: @escaping (_ value: Data, _ key: String) throws -> Void,
-    remove: @escaping (_ key: String) throws -> Void,
+    getString: @escaping (_ key: Key) throws -> String?,
+    getData: @escaping (_ key: Key) throws -> Data?,
+    setString: @escaping (_ value: String, _ key: Key) throws -> Void,
+    setData: @escaping (_ value: Data, _ key: Key) throws -> Void,
+    remove: @escaping (_ key: Key) throws -> Void,
     removeAll: @escaping () throws -> Void,
-    contains: @escaping (_ key: String) throws -> Bool
+    contains: @escaping (_ key: Key) throws -> Bool
   ) {
     self.getString = getString
     self.getData = getData
@@ -26,4 +26,27 @@ public struct KeychainClient {
     self.removeAll = removeAll
     self.contains = contains
   }
+
+  /// Type safe key used for looking up the Keychain.
+  ///
+  /// Example:
+  /// ```swift
+  /// extension KeychainClient.Key {
+  ///   static let currentSession = Key("current_session")
+  /// }
+  ///
+  /// let keychain = KeychainClient.live(...)
+  /// let data = try keychain.getData(.currentSession)
+  /// ```
+  public struct Key: RawRepresentable {
+    public var rawValue: String
+
+    public init(rawValue: String) {
+      self.rawValue = rawValue
+    }
+
+    public init(_ rawValue: String) {
+      self.init(rawValue: rawValue)
+    }
+  }
 }

Sources/ComposableKeychain/Live.swift

@@ -1,16 +1,18 @@
 import KeychainAccess
 
 extension KeychainClient {
-
+  /// Creates a live implementation of the KeychainClient.
+  /// - Parameter keychain: Configured Keychain instance to use.
+  /// - Returns: The KeychainClient.
   public static func live(keychain: Keychain) -> KeychainClient {
     return KeychainClient(
-      getString: { try keychain.get($0) },
-      getData: { try keychain.getData($0) },
-      setString: { try keychain.set($0, key: $1) },
-      setData: { try keychain.set($0, key: $1) },
-      remove: { try keychain.remove($0) },
+      getString: { try keychain.get($0.rawValue) },
+      getData: { try keychain.getData($0.rawValue) },
+      setString: { try keychain.set($0, key: $1.rawValue) },
+      setData: { try keychain.set($0, key: $1.rawValue) },
+      remove: { try keychain.remove($0.rawValue) },
       removeAll: { try keychain.removeAll() },
-      contains: { try keychain.contains($0) }
+      contains: { try keychain.contains($0.rawValue) }
     )
   }
 }

Sources/ComposableKeychain/Mocks.swift

@@ -1,4 +1,6 @@
 extension KeychainClient {
+  /// A KeychainClient implementation that does nothing when called.
+  /// Can be used on Xcode Previews.
   public static let noop = KeychainClient(
     getString: { _ in nil },
     getData: { _ in nil },
@@ -14,6 +16,8 @@ extension KeychainClient {
   import XCTestDynamicOverlay
 
   extension KeychainClient {
+    /// A KeychainClient implementation that fails when called.
+    /// Used for testing purposes and available only in DEBUG builds.
     public static let failing = KeychainClient(
       getString: { key in
         XCTFail("\(Self.self).getString(\(key)) is unimplemented")