iOS skills setValue:forKey:

除左之前係針對UI elements 去學
仲有啲特別野係可以其他地方都用到

[self setValue:someValues forKey:keyNameOrVariable];
呢個message係一啲regular 既variable name好有用
例如你有五個NSArray

NSArray arr1 =...
NSArray arr2 =...
NSArray arr3 =...
NSArray arr4 =...
NSArray arr5 =... 

而每個NSArray 都要init 同比啲elements

for (int i = 1 ; i <=5 ; i++)
{
initialize..
initialize needed objects..
NSArray *tempArray = [[NSArray alloc] initWithObjects:obj1, obj2, obj3 , .. nil];f
NSString *arrayName = [[NSSting alloc] initWithFormat:@"arr%d" , i];

[self setValue:tempArray forKey:arrayName];
}
咁就set 曬全部array

P.S. From Beginning iOS 5 Development Apress Chapter 10

Instead of calling a setDelegate: method, we're using something called key-value coding (KVC), which allows us to use getters and setters on any object indirectly, using strings instead of method names. KVC is a core feature of the Cocoa Touch frameworks, and its main methods—setValue:forKey: and valueForKey:—are built into NSObject, so they're available everywhere. We're not covering this topic in detail in this book, but are using it briefly here.

Why are we using KVC here instead of just setting the delegate directly? One of the benefits of KVC is that it frees us from knowing the specifics of other classes' interfaces, which leads to less tightly coupled code. If we wanted to call the method directly, we would need to declare an interface of some kind that included the setDelegate: method, and cast our destination variable to be a type that implemented that method. Using KVC, our code doesn't need to know anything about the setDelegate: method (apart from the fact that the receiver responds to it), so we don't need to have any declared interface to it. BIDTaskListController doesn't import BIDTaskDetailController's header, and, in fact, doesn't even know that it exists, and that's a good thing! In general, the fewer dependencies you have between classes, the better. Properly applied, KVC can help you move your code in that direction.