KVC/KVO, kvckvo

KVC/KVO, kvckvo

1 // KVC (Key Value Coding) 2 // assign values to attributes of an object, 3 Student * stu = [[Student alloc] init]; 4 [stu setValue: @ "xiaowang" forKey: @ "name"]; 5 NSLog (@ "% @", stu. name); 6 7 8 // KVO (Key Value Observer) 9 // Add the observer 10 to the student object // The first parameter is who observes the student 11 // The second parameter is the observed student's attribute 12 // The third parameter is the observation mode 13 14 // instantiate the Student object 15 stu = [[Student alloc] init]; 16 [stu setValue: @ "zhangsan" forKey: @ "name"]; 17 [stu addObserver: self forKeyPath: @ "name" options: available | NSKeyValueObservingOptionOld context: nil]; 18 // set the name attribute of the student object to xiaowang19 [stu setValue: @ "xiaowang" forKey: @ "name"];

// The Observer calls this method when it finds that the observed attribute is changed. The observer writes this method to the observer. m-(void) observeValueForKeyPath :( NSString *) keyPath ofObject :( id) object change :( NSDictionary *) change context :( void *) context {NSLog (@ "new: % @", [change objectForKey: @ "new"]); NSLog (@ "old: % @", [change objectForKey: @ "old"]);}