IOS KVC运用代码详解
一 KVC简介
KVC，即是指 NSKeyValueCoding，提供一种机制来间接访问对象的属性。常用于字典转模型，或者用于模型转字典，继承于NSObject 类，子类可用直接使用。
二 KVC赋值
//可以给当前对象属性赋值 - (void)setValue:(id)value forKey:(NSString *)key; //可以给对象的属性的属性赋值（推荐使用） - (void)setValue:(id)value forKeyPath:(NSString *)keyPath; //字典转对象 - (void)setValuesForKeysWithDictionary:(NSDictionary *)keyedValues;
注意：
forKey只能给当前对象属性赋值。
例如：[self setVale:@"wlx" forkey:@"name"]。
forKeyPath 可以给对象的属性的属性赋值。
例如：[self setVale:@"thinkpad" forkeypath:@"person.computer"]。
二 字典转模型
- (void)setValuesForKeysWithDictionary:(NSDictionary *)keyedValues;
注意：要求字典中的key 和对象属性要求一样
三 模型转字典
- (NSDictionary *)dictionaryWithValuesForKeys:(NSArray *)keys;
//实例:
NSDictionary *dic = [self.dataArray dictionaryWithValuesForKeys:@[@"name",@"age"]];
for (int i =0 ; i<dic.count; i++) {
NSLog(@"%@", [dic objectForKey:[dic allKeys][i]]);
}
四 KVC取值
//只能获取对象属性的值 - (id)valueForKey:(NSString *)key; //可以获取对象属性的属性的值（推荐使用） - (id)valueForKeyPath:(NSString *)keyPath;
五 KVC运算
KVC 可用进行简单的运算，例如 sum avg min 的运算。
[array valueForKeyPath:@"@sum.age"];
NSLog(@"sum=%@",[self.dataArray valueForKeyPath:@"@sum.age"]); NSLog(@"avg=%@",[self.dataArray valueForKeyPath:@"@avg.age"]); NSLog(@"min=%@",[self.dataArray valueForKeyPath:@"@min.age"]);
六 注意事项
KVC需要把字符串属性名称转换后才能赋值,调用的set方法，性能消耗较高
七 代码
7.1 ViewController
#import "ViewController.h"
#import "Cat.h"
#import "Person.h"
@interface ViewController ()
@property (nonatomic,strong) NSArray *dataArray;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
/** KVC 测试 **/
//1.KVC 设置Cat 值
NSLog(@"=====KVC 设置Cat 值 字段转模型====");
for (int i=0; i<self.dataArray.count; i++) {
Cat *cat = (Cat *)self.dataArray[i];
NSLog(@"%@",cat.name);
}
//2 测试 forKey forKeyPath 区别
NSLog(@"=====forKey forKeyPath valueForKey valueForKeyPath 区别 ====");
//2.1 创建 person 对象
Person *p = [[Person alloc]init];
//2.2 创建 cat 对象
Cat *cat = self.dataArray[0];
//2.3 把 cat 赋值给 persion 对象中的 cat 属性
p.cat = cat;
//2.4 设置 person name 属性的值
[p setValue:@"卧龙小" forKey:@"name"];
//2.5 设置 persion cat 对象的 name 属性
//[p setValue:[cat name] forKey:@"cat.name"]; //报错NSUnknownKeyException
[p setValue:@"cat4" forKeyPath:@"cat.name"];
NSLog(@"%@ - %@",[p valueForKey:@"name"],[p valueForKeyPath:@"cat.name"]);
//3 模型转字典
NSLog(@"=====模型转字典 ====");
NSDictionary *dic = [self.dataArray dictionaryWithValuesForKeys:@[@"name",@"age"]];
for (int i =0 ; i<dic.count; i++) {
NSLog(@"%@", [dic objectForKey:[dic allKeys][i]]);
}
//4 kvc运算
NSLog(@"=====kvc运算====");
NSLog(@"sum=%@",[self.dataArray valueForKeyPath:@"@sum.age"]);
NSLog(@"avg=%@",[self.dataArray valueForKeyPath:@"@avg.age"]);
NSLog(@"min=%@",[self.dataArray valueForKeyPath:@"@min.age"]);
}
/**
* 懒加载
*/
-(NSArray *)dataArray
{
// 1.获取文件
NSBundle *bundle = [NSBundle mainBundle];
NSArray *array = [NSArray arrayWithContentsOfFile:[bundle pathForResource:@"cat.plist" ofType:nil]];
NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:array.count];
// 2.封装数据
for (NSDictionary *dic in array) {
Cat *cat = [Cat catWithDic:dic];
[mutableArray addObject:cat];
}
// 3.返回数据
_dataArray = mutableArray;
return _dataArray;
}
@end
7.2Cat类
===cat.h===
@interface Cat : NSObject
/**
* 年龄
*/
@property (nonatomic,assign)NSInteger age;
/**
* 名字
*/
@property (nonatomic,copy)NSString *name;
/**
* 构造方法
*
* @param dic <#dic description#>
*
* @return <#return value description#>
*/
-(instancetype)initWithDic:(NSDictionary *)dic;
+(instancetype)catWithDic:(NSDictionary *)dic;
@end
===cat.m===
#import <Foundation/Foundation.h>
#import "Cat.h"
@implementation Cat
-(instancetype)initWithDic:(NSDictionary *)dic
{
if (self = [super init]) {
/** KVC 字典转模型 **/
//1 通过 setValue 方法
//[self setValue:dic[@"name"] forKey:@"name"];
//[self setValue:dic[@"age"] forKeyPath:@"age"];
//2 字典转模型
[self setValuesForKeysWithDictionary:dic];
}
return self;
}
+(instancetype)catWithDic:(NSDictionary *)dic
{
return [[self alloc]initWithDic:dic];
}
@end
7.3 person类
===person.h=== #import "Cat.h" @interface Person : NSObject /** * 名字 */ @property (nonatomic,copy)NSString *name; /** * 拥有的猫 */ @property (nonatomic,strong)Cat *cat; @end ===person.m=== #import <Foundation/Foundation.h> #import "Person.h" @implementation Person @end
7.4 输出
2014-12-29 00:42:03.814 22KVC测试[2484:149139] =====KVC 设置Cat 值 字段转模型==== 2014-12-29 00:42:03.815 22KVC测试[2484:149139] cat1 2014-12-29 00:42:03.815 22KVC测试[2484:149139] cat2 2014-12-29 00:42:03.815 22KVC测试[2484:149139] cat3 2014-12-29 00:42:03.816 22KVC测试[2484:149139] =====forKey forKeyPath valueForKey valueForKeyPath 区别 ==== 2014-12-29 00:42:03.816 22KVC测试[2484:149139] 卧龙小 - cat4 2014-12-29 00:42:03.816 22KVC测试[2484:149139] =====模型转字典 ==== 2014-12-29 00:42:03.816 22KVC测试[2484:149139] ( cat1, cat2, cat3 ) 2014-12-29 00:42:03.816 22KVC测试[2484:149139] ( 5, 7, 5 ) 2014-12-29 00:42:03.816 22KVC测试[2484:149139] =====kvc运算==== 2014-12-29 00:42:03.816 22KVC测试[2484:149139] sum=17 2014-12-29 00:42:03.817 22KVC测试[2484:149139] avg=5.6666666666666666666666666666666666666 2014-12-29 00:42:03.817 22KVC测试[2484:149139] min=5