KVC- Key-Value Coding.
KVO Key-Value Observing.
KVC是Objective-C提供的一种对象属性的访问机制。对于有面向对象编程习惯的程序员，这是别开生面的方式：不需要在源码通过特殊标志符“." 或 "->"来访问属性；KVC只需要在运行时提供属性名/路径名，就能获得某属性的值。
范例：
@interface Student : NSObject
{
NSString *name;
}
@end
@implementation Student
@end
///////通过Key访问属性name
Student * stu=[ [Student alloc] init];
[stu setValue:@"Ken Wu" forKey:@"name"];
NSString *newname = [stu valueForKey:@"name"]; //newname的值就是“Ken Wu"。
如果是复杂的对象，如以下Student有课程信息，记录其分数。
@interface Course : NSObject
{
NSString *name;
float score;
}
@end
@implementation Course
@end
@interface Student : NSObject
{
NSString *name;
Course *course;
}
@end
@implementation Student
@end
//////通过KeyPath访问课程分数
Student * stu=[ [Student alloc] init];
[stu setValue:@"Ken Wu" forKey:@"name"];
NSString *newname = [stu valueForKey:@"name"]; //newname的值就是“Ken Wu"。
[stu setValue:@"Ken Wu" forKey:@"name"];
Course *course =[ [Course alloc] init];
[stu setValue:course forKey:@"course"];
[stu setValue:@"科目1" forKeyPath:@"course.name"];
[stu setValue: 99.9 forKeyPath:@"course.score"];
float score = [stu valueForKeyPath:@"corse.score"]; //score的值就是 99.9
以上就是KVC的内容
KVO则在此基础上，对对象属性的变化增加了观察机制。一旦值发生了改变，就会回调已知函数
observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context
范例：
[stu addObserver:self forKeyPath:@"corse.score" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];
-(void)
observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context{
If([keyPath isEqualToString:@"corse.score"]){
float newScore = [change objectForKey:@"new"];
float oldScore = [change objectForKey:@"old"];
If(newScore > oldScore){
NSLog(@"You made a progress!");
}
Else {
NSLog(@"You need move luck!");
}
}
}
以上就是KVO的内容