一、KVC简单介绍
KVC key valued coding 键值编码
KVC通过键值间接编码
补充：
与KVC相对的时KVO，即key valued observer 键值观察。监听某一个模型的属性，只要模型属性的值一变化就通知你。
二、代码颜色
1> 通过KVC设置值 setValue: forKey：
1，1>
@interface Person : NSObject @property (nonatomic, copy) NSString *name; @property (nonatomic, assign) int age; @property (nonatomic, strong) Book *book; @end @implementation Person @end int main(int argc, const char * argv[]) { @autoreleasepool { Person *p1 = [[Person alloc] init]; [p1 setValue:@"zhangsan" forKey:@"name"]; p1.age = 18; NSLog(@"name = %@, age = %d", p1.name, p1.age); } return 0; }
通过执行结果可以看到这个方法通过对象的属性值设置value。
1,2> 通过KVC设置值 setValue: forKeyPath：
@interface Person : NSObject @property (nonatomic, copy) NSString *name; @property (nonatomic, assign) int age; @property (nonatomic, strong) Book *book; @end @implementation Person @end int main(int argc, const char * argv[]) { @autoreleasepool { Person *p1 = [[Person alloc] init]; [p1 setValue:@"zhangsan" forKeyPath:@"name"]; p1.age = 18; NSLog(@"name = %@, age = %d", p1.name, p1.age); } return 0; }
可以看到两个方法执行效果一样，
[setValue:@"zhangsan" forKeyPath:@"name"];
要看到这个方法的好处，可以看下面这个例子：
1.3>
#import <Foundation/Foundation.h> @interface Book : NSObject @property (nonatomic, copy) NSString *bookName; @end @implementation Book @end @interface Person : NSObject @property (nonatomic, copy) NSString *name; @property (nonatomic, assign) int age; @property (nonatomic, strong) Book *book; @end @implementation Person @end int main(int argc, const char * argv[]) { @autoreleasepool { Person *p1 = [[Person alloc] init]; Book *b1 = [[Book alloc] init]; p1.book = b1; [p1 setValue:@"同桌的你" forKeyPath:@"book.bookName"]; NSLog(@"bookName = %@", b1.bookName); } return 0; }
用KVC取一个嵌套层次很深的路径的时候，只要诶它一个路径就能把想要的属性给拿出来。（.可以理解为路径。一直一直进入）。能够帮助我们很方便的编码。
2,通过KVC取值：
#import <Foundation/Foundation.h> @interface Book : NSObject @property (nonatomic, copy) NSString *bookName; @end @implementation Book @end @interface Person : NSObject @property (nonatomic, copy) NSString *name; @property (nonatomic, assign) int age; @property (nonatomic, strong) Book *book; @end @implementation Person @end int main(int argc, const char * argv[]) { @autoreleasepool { Person *p1 = [[Person alloc] init]; Book *b1 = [[Book alloc] init]; b1.bookName = @"同桌的你"; p1.book = b1; NSString *bookName = [p1 valueForKeyPath:@"book.bookName"]; NSLog(@"bookName = %@", bookName); } return 0; }
结果：
当然我们也可以通过valueForKey:取值不过只能取person对象的属性的值，不能取到book对象中的属性值
3，将person对象放入到数组中，通过数组取的person对象中属性的值
代码：
@interface Person : NSObject @property (nonatomic, copy) NSString *name; @property (nonatomic, assign) int age; @property (nonatomic, strong) Book *book; @end @implementation Person @end int main(int argc, const char * argv[]) { @autoreleasepool { Person *p1 = [[Person alloc] init]; p1.name = @"zhangsan"; Person *p2 = [[Person alloc] init]; p2.name = @"lisi"; NSArray *array = @[p1, p2]; NSArray *name = [array valueForKeyPath:@"name"]; NSLog(@"%@", name); } return 0; }
结论：将对象放入到数组中，可以通过数组的valueForKeyPath：方法取出数组中存放对象的属性值，返回一个存放属性值的数组对象
4>KVC在字典中的应用
4.1 可以将字典中的键对应的值赋给对象的属性值
@interface Person : NSObject @property (nonatomic, copy) NSString *name; @property (nonatomic, assign) int age; @property (nonatomic, strong) Book *book; @end @implementation Person @end int main(int argc, const char * argv[]) { @autoreleasepool { Person *p1 = [[Person alloc] init]; NSDictionary *dic = @{@"name":@"zhangsan"}; [p1 setValuesForKeysWithDictionary:dic]; NSLog(@"%@", p1.name); } return 0; }
4.2 可以将对象的属性值赋给字典键对应的值
@interface Person : NSObject @property (nonatomic, copy) NSString *name; @property (nonatomic, assign) int age; @property (nonatomic, strong) Book *book; @end @implementation Person @end int main(int argc, const char * argv[]) { @autoreleasepool { Person *p1 = [[Person alloc] init]; p1.name = @"zhangsan"; p1.age = 19; NSDictionary *dic = [p1 dictionaryWithValuesForKeys:@[@"name", @"age"]]; NSLog(@"%@", dic); } return 0; }
用KVC取一个嵌套层次很深的路径的时候，只要诶它一个路径就能把想要的属性给拿出来。（.可以理解为路径。一直一直进入）。能够帮助我们很方便的编码