KVC –key value Coding，可以让我们通过键值编码的形式进行属性值的赋值
参考苹果官网的图。。
1.KVC
定义一个Person类
.h文件
1:#import <Foundation/Foundation.h>
2:
3:@interfacePerson : NSObject
4:{
5:NSString *name;
6:}
7:
8:@end
.csharpcode, .csharpcodePRe
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp{ background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }.m文件
1:#import"Person.h"
2:
3:@implementationPerson
4:
5:@end
.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }
通过普通的获取属性的方法是无法对name进行赋值和取值操作的，这种情况可以通过KVC来进行设置和取值
1:- (void)viewDidLoad {
2:[super viewDidLoad];
3:// Do any additional setup after loading the view, typically from a nib.
4:Person person=[[Person alloc]init];
5:[person setValue:@"keith"forKey:@"name"];
6:NSLog(@"name is %@",[person valueForKey:@"name"]);
7:}
输出：
2014-11-26 21:51:12.237 KVCtest[543:10453] name is keith
.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }赋值用setValue:forKey:
取值用 valueForKey:
2.键路径
如果类中包含其他的类怎么办呢，访问这个类的属性怎么办呢。可以使用setValue: forKeyPath: 和valueForKeyPath设置和获取
如定义一个car
.h文件
#import<Foundation/Foundation.h>@interfaceCar : NSObject
{
NSString*carname;
}@end
将Person的.h改成
#import<Foundation/Foundation.h>@classCar;@interfacePerson : NSObject
{
NSString*name;
Car*hiscar;
}-(id)init;@end
.m为
#import"Person.h"#import"Car.h"@implementationPerson-(id)init{if(self=[super init]) {
hiscar=[[Car alloc]init];
}returnself;
}@end
这里实现了car的实例化，如果不这么做在键值编程时候hiscar因为没有初始化而出现无法赋值的情况
调用:
- (void)viewDidLoad {
[super viewDidLoad];//Do any additional setup after loading the view, typically from a nib.Person *person=[[Person alloc]init];
[person setValue:@"keith"forKey:@"name"];
[person setValue:@"QQ"forKeyPath:@"hiscar.carname"];
NSLog(@"name is %@,hiscar is %@",[person valueForKey:@"name"],[person valueForKeyPath:@"hiscar.carname"]);/*或者这样*/Car*car=[[Car alloc]init];
[car setValue:@"BeiKy"forKey:@"carname"];
[person setValue:car forKey:@"hiscar"];
NSLog(@"name is %@,hiscar is %@",[person valueForKey:@"name"],[person valueForKeyPath:@"hiscar.carname"]);
}
输出结果
2014-11-26 22:45:47.392 KVCtest[1031:25564] name is keith,hiscar is QQ
2014-11-26 22:45:47.394 KVCtest[1031:25564] name is keith,hiscar is BeiKy
3.类型封装和转换
再次修改Person.h文件
#import<Foundation/Foundation.h>@classCar;@interfacePerson : NSObject
{
NSString*name;
Car*hiscar;
NSInteger age;//增加一个年龄类型是NSInteger}-(id)init;@end
那么如何在设置的时候会发生什么呢？
- (void)viewDidLoad {
[super viewDidLoad];//Do any additional setup after loading the view, typically from a nib.Person *person=[[Person alloc]init];
[person setValue:@"keith"forKey:@"name"];
[person setValue:@"QQ"forKeyPath:@"hiscar.carname"];
[person setValue:@"24"forKeyPath:@"age"];//为年龄赋值NSLog(@"name is %@, is %@ old ,hiscar is %@",[person valueForKey:@"name"],[person valueForKey:@"age"],[person valueForKeyPath:@"hiscar.carname"]);
}
结果是:
2014-11-26 22:56:08.873 KVCtest[1086:27956] name is keith, is 24 old ,hiscar is QQ
4.操作集合
在Person中添加一个otherPerson
#import<Foundation/Foundation.h>@classCar;@interfacePerson : NSObject
{
NSString*name;
Car*hiscar;
NSInteger age;
NSMutableArray*otherPerson;
}-(id)init;@end
属性.@sum.属性，还有@count,@avg,@max.@min
-(void)kvcCollection{
Person*person=[[Person alloc]init];
[person setValue:@"keith"forKey:@"name"];
Person*person1=[[Person alloc]init];
Person*person2=[[Person alloc]init];
Person*person3=[[Person alloc]init];
Person*person4=[[Person alloc]init];
NSMutableArray*others=[[NSMutableArray alloc]initWithObjects:person1,person2,person3,person4, nil];
NSInteger agenum=20;for(Person *pinothers) {
[self setage:p age:[[NSString alloc]initWithFormat:@"%ld",agenum++]];
}
[person setValue:others forKey:@"otherPerson"];
NSLog(@"other's age is %@",[person valueForKeyPath:@"otherPerson.age"]);
NSLog(@"the avg age is %@",[person valueForKeyPath:@"otherPerson.@avg.age"]);
NSLog(@"the sum age is %@",[person valueForKeyPath:@"otherPerson.@sum.age"]);
NSLog(@"the count person is %@",[person valueForKeyPath:@"otherPerson.@count.age"]);
NSLog(@"the min age is %@",[person valueForKeyPath:@"otherPerson.@min.age"]);
NSLog(@"the max age is %@",[person valueForKeyPath:@"otherPerson.@max.age"]);
}-(void)setage:(Person *)person age:(NSString *)age{
[person setValue: age forKey:@"age"];
}
输出
2014-11-26 23:51:00.180 KVCtest[1346:42300] other's age is (
20,
21,
22,
23
)
2014-11-26 23:51:00.183 KVCtest[1346:42300] the avg age is 21.5
2014-11-26 23:51:00.183 KVCtest[1346:42300] the sum age is 86
2014-11-26 23:51:00.184 KVCtest[1346:42300] the count person is 4
2014-11-26 23:51:00.184 KVCtest[1346:42300] the min age is 20
2014-11-26 23:51:00.184 KVCtest[1346:42300] the max age is 23
本文参考容芳志博客，感谢这位博友
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