default implementations for Diffable protocol

DataSource/Diffable.swift

@@ -15,14 +15,17 @@ public protocol Diffable {
     func isEqualToDiffable(_ other: Diffable?) -> Bool
 }
 
-extension String: Diffable {
-    
-    public var diffIdentifier: String {
-        return self
+public extension Diffable where Self: Hashable {
+
+    var diffIdentifier: String {
+        return String(hashValue)
     }
+}
+
+public extension Diffable where Self: Equatable {
 
-    public func isEqualToDiffable(_ other: Diffable?) -> Bool {
-        guard let other = other as? String else { return false }
+    func isEqualToDiffable(_ other: Diffable?) -> Bool {
+         guard let other = other as? Self else { return false }
         return self == other
     }
 }

Example/ViewControllers/Examples/DiffViewController.swift

@@ -70,23 +70,19 @@ class DiffViewController: UITableViewController {
 
 // MARK: - Diff Item
 
-struct DiffItem {
+struct DiffItem: Hashable, Equatable {
 
     let value: Int
     let text: String
-    let diffIdentifier: String
 
     init(_ value: Int, text: String) {
         self.value = value
         self.text = text
-        self.diffIdentifier = String(value)
     }
-}
-
-extension DiffItem: Diffable {
 
-    public func isEqualToDiffable(_ other: Diffable?) -> Bool {
-        guard let other = other as? DiffItem else { return false }
-        return self.text == other.text
+    var hashValue: Int {
+        return value
     }
 }
+
+extension DiffItem: Diffable { }

Example/ViewControllers/Examples/RandomPersonsViewController.swift

@@ -128,11 +128,6 @@ extension Person: Diffable {
     public var diffIdentifier: String {
         return fullName
     }
-
-    func isEqualToDiffable(_ other: Diffable?) -> Bool {
-        guard let other = other as? Person else { return false }
-        return self == other
-    }
 }
 
 extension Person: CustomStringConvertible {