iOS KVC(Key-Value Coding)

iOS KVC(Key-Value Coding)
常見使用方法：擷取值
valueForKey: 根據屬性名稱取值 valueForKeyPath: 根據路徑取值(如：[person valueForKeyPath:@”car.price”]) valueForUndefinedKey 預設實現是拋出異常，可以重寫這個函數做錯誤處理 ( 比較少用 ) 修改值
setValue:forKey: 根據屬性設值 setValue:forKeyPath: 根據路徑設值 setValue:forUndefinedKey: setNilValueForKey: 當對非類對象屬性設定nil時，調用，預設拋出異常 字典轉模型
setValuesForKeysWithDictionary: 字典轉模型上代碼：

定義一個HSCar類

////  HSCar.h//  KVC////  Created by hans on 15/7/13.//  Copyright © 2015年 hans. All rights reserved.//#import @interface HSCar : NSObject/** 名字 */@property (nonatomic, copy) NSString *name;/** 價格 */@property (nonatomic, assign) double price;@end

定義一個HSBook類

////  HSBook.h//  KVC////  Created by hans on 15/7/13.//  Copyright © 2015年 hans. All rights reserved.//#import @interface HSBook : NSObject/** 書名 */@property (nonatomic, copy) NSString *name;/** 價格 */@property (nonatomic, assign) double price;@end

定義一個HSPerson類

////  HSPerson.h//  KVC////  Created by hans on 15/7/13.//  Copyright © 2015年 hans. All rights reserved.//#import @class HSCar;@interface HSPerson : NSObject/** 名字 */@property (nonatomic, copy) NSString *name;/** 年齡 */@property (nonatomic, copy) NSString *age;/** 車 */@property (nonatomic, strong) HSCar *car;@end

////  HSPerson.m//  KVC////  Created by hans on 15/7/13.//  Copyright © 2015年 hans. All rights reserved.//#import HSPerson.h@implementation HSPerson{    // 體重    double _weight;}- (void)showWeight{    NSLog(@weight: %f, _weight);}@end

在ViewController實現

////  ViewController.m//  KVC////  Created by hans on 15/7/13.//  Copyright © 2015年 hans. All rights reserved.//#import ViewController.h#import HSPerson.h#import HSCar.h#import HSBook.h@interface ViewController ()@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    HSPerson *person = [HSPerson new];    person.name = @hans;    person.age = 23;    person.car = [HSCar new];    person.car.name = @蘭博基尼;    person.car.price = 10000000.0;    /** valueForKey: */    NSLog(@name: %@ age: %@, [person valueForKey:@name], [person valueForKey:@age]);    // 2015-07-13 22:32:02.356 KVC[54356:872650] name: hans age: 23    /** valueForKeyPath: */    NSLog(@name：%@ price： %@, [person valueForKeyPath:@car.name], [person valueForKeyPath:@car.price]);    // 2015-07-13 22:51:27.075 KVC[54669:885579] name：蘭博基尼 price： 10000000    /** setValue:forKey: */    [person setValue:@hanshhh forKey:@name];    [person setValue:@100 forKey:@age];    NSLog(@name: %@ age: %@, [person valueForKey:@name], [person valueForKey:@age]);    // 2015-07-13 22:53:54.876 KVC[54709:886954] name: hanshhh age: 100    /** setValue:forKeyPath: */    [person setValue:@法拉利 forKeyPath:@car.name];    [person setValue:@(9999999) forKeyPath:@car.price];    NSLog(@name：%@ price： %@, [person valueForKeyPath:@car.name], [person valueForKeyPath:@car.price]);    // 2015-07-13 22:56:36.336 KVC[54767:888926] name：法拉利 price： 9999999    /** 更改私人屬性 */    [person setValue:@(120) forKeyPath:@_weight];    [person showWeight];    // 2015-07-13 23:01:15.151 KVC[54847:892122] weight: 120.000000    /** 字典轉模型 */    // 1.簡單轉換    NSDictionary *dict1 = @{                           @name  : @漢斯,                           @age : @23,                           };    [person setValuesForKeysWithDictionary:dict1];    NSLog(@name : %@, age : %d, person.name, person.age);    // 2015-07-13 23:04:20.298 KVC[54943:895092] name : 漢斯, age : 23    // 2.複雜模型轉換(注意：person.car不能轉換，會變為字典對象，其實就是簡單的指標賦值而已)    NSDictionary *dict2 = @{                           @name  : @漢斯哈哈哈,                           @age : @23,                           @car : @{                                   @name : @蘭博基尼,                                   @price : @10000000                                   },                            };    [person setValuesForKeysWithDictionary:dict2];    NSLog(@%@, person.car);//    2015-07-13 23:10:32.310 KVC[55019:899474] {//        name = U5170U535aU57faU5c3c;//        price = 10000000;//    }    /** 其他運算 */    HSBook *book1 = [HSBook new];    book1.name = @結網;    book1.price = 51.0;    HSBook *book2 = [HSBook new];    book2.name = @失控;    book2.price = 40.0;    HSBook *book3 = [HSBook new];    book3.name = @異類;    book3.price = 60.0;    person.books = @[book1, book2, book3];    NSLog(@%@, [person.books valueForKeyPath:@@count]);    NSLog(@%@, [person.books valueForKeyPath:@@avg.price]);    NSLog(@%@, [person.books valueForKeyPath:@@min.price]);    NSLog(@%@, [person.books valueForKeyPath:@@max.price]);//    2015-07-13 23:20:43.434 KVC[55171:905643] 3//    2015-07-13 23:20:43.434 KVC[55171:905643] 50.333333333333333333333333333333333333//    2015-07-13 23:20:43.435 KVC[55171:905643] 40//    2015-07-13 23:20:43.435 KVC[55171:905643] 60}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end