keep default model value for optimization

Author: CoderMJLee

KakaJSON/Convert/Convertible.swift

@@ -264,7 +264,9 @@ extension Convertible {
             }
 
             // try to convert newValue to propertyType
-            guard let value = Values.value(newValue, propertyType) else {
+            guard let value = Values.value(newValue,
+                                           propertyType,
+                                           property.get(from: model)) else {
                 property.set(newValue, for: model)
                 continue
             }

KakaJSON/Convert/Values.swift

@@ -12,15 +12,17 @@ import CoreGraphics
 #endif
 
 public struct Values {
-    static func value(_ val: Any?, _ type: Any.Type) -> Any? {
+    static func value(_ val: Any?,
+                      _ type: Any.Type,
+                      _ defaultValue: @autoclosure () -> Any? = nil) -> Any? {
         guard let v = val.kj_value else { return nil }
         if Swift.type(of: v) == type { return v }
         if v is NSNull { return nil }
 
         switch type {
         case is NumberValue.Type: return _number(v, type)
         case is StringValue.Type: return _string(v, type)
-        case let ct as Convertible.Type: return _model(v, ct)
+        case let ct as Convertible.Type: return _model(v, ct, defaultValue)
         case is DateValue.Type: return _date(v)
         case is ArrayValue.Type: return _array(v, type)
         case is DictionaryValue.Type: return _dictionary(v, type)
@@ -73,8 +75,14 @@ private extension Values {
         return lower
     }
 
-    static func _model(_ value: Any, _ type: Convertible.Type) -> Convertible? {
+    static func _model(_ value: Any,
+                       _ type: Convertible.Type,
+                       _ defaultValue: () -> Any?) -> Convertible? {
         guard let json = value as? [String: Any] else { return nil }
+        if var model = defaultValue().kj_value as? Convertible {
+            model.kj_convert(from: json)
+            return model
+        }
         return json.kj.model(type: type)
     }
 

KakaJSONTests/JSON_To_Model/JTM_03_NestedModel.swift

@@ -72,6 +72,48 @@ class JTM_03_NestedModel: XCTestCase {
         XCTAssert(person.dogs?["dog1"]?.name == dogs[1].name)
         XCTAssert(person.dogs?["dog1"]?.age == dogs[1].age)
     }
+    
+    func testDefaultValue() {
+        struct Car: Convertible {
+            var name: String = ""
+            var price: Double = 0.0
+        }
+        
+        class Dog: Convertible {
+            var name: String = ""
+            var age: Int = 0
+            required init() {}
+            init(name: String, age: Int) {
+                self.name = name
+                self.age = age
+            }
+        }
+        
+        struct Person: Convertible {
+            var name: String = ""
+            // KakaJSON will use your defaultValue instead of creating a new model
+            // KakaJSON will not creat a new model again if you already have a default model value
+            var car: Car = Car(name: "Bently", price: 106.5)
+            var dog: Dog = Dog(name: "Larry", age: 5)
+        }
+        
+        let json: [String: Any] = [
+            "name": "Jake",
+            "car": ["price": 305.6],
+            "dog": ["name": "Wangwang"]
+        ]
+        
+        let person = json.kj.model(Person.self)
+        XCTAssert(person.name == "Jake")
+        // keep defaultValue
+        XCTAssert(person.car.name == "Bently")
+        // use value from json
+        XCTAssert(person.car.price == 305.6)
+        // use value from json
+        XCTAssert(person.dog.name == "Wangwang")
+        // keep defaultValue
+        XCTAssert(person.dog.age == 5)
+    }
 
     func testRecursive() {
         class Person: Convertible {

README.md

@@ -50,6 +50,7 @@ Or you can login Xcode with your GitHub account. just search **KakaJSON**.
   - [JSONData](#jsondata)
   - [Nested Model 1](#nested-model-1)
   - [Nested Model 2](#nested-model-2)
+  - [Nested Model 3](#nested-model-3)
   - [Recursive](#recursive)
   - [Generic](#generic)
   - [Model Array](#model-array)
@@ -487,6 +488,49 @@ XCTAssert(book?.name == "Fast C++")
 XCTAssert(book?.price == 666.6)
 ```
 
+### Nested Model3
+```swift
+struct Car: Convertible {
+    var name: String = ""
+    var price: Double = 0.0
+}
+
+class Dog: Convertible {
+    var name: String = ""
+    var age: Int = 0
+    required init() {}
+    init(name: String, age: Int) {
+        self.name = name
+        self.age = age
+    }
+}
+
+struct Person: Convertible {
+    var name: String = ""
+    // KakaJSON will use your defaultValue instead of creating a new model
+    // KakaJSON will not creat a new model again if you already have a default model value
+    var car: Car = Car(name: "Bently", price: 106.5)
+    var dog: Dog = Dog(name: "Larry", age: 5)
+}
+
+let json: [String: Any] = [
+    "name": "Jake",
+    "car": ["price": 305.6],
+    "dog": ["name": "Wangwang"]
+]
+
+let person = json.kj.model(Person.self)
+XCTAssert(person.name == "Jake")
+// keep defaultValue
+XCTAssert(person.car.name == "Bently")
+// use value from json
+XCTAssert(person.car.price == 305.6)
+// use value from json
+XCTAssert(person.dog.name == "Wangwang")
+// keep defaultValue
+XCTAssert(person.dog.age == 5)
+```
+
 ### Recursive
 ```swift
 class Person: Convertible {