Question

I need to move the same method from 4 different classes to the superclass.
Such methods are exactly the same except for the type of a variable declared in them:

For example, in the method in the first class I have

FirstClass var = [[FirstClass alloc] init]

in the second class

SecondClass var = [[SecondClass alloc] init]

and so on.

What’s the best way to implement this variation in the superclass ?

Should I use NSClassFromString in the superclass and get each string from each method in the subclasses?

thanks

Answer 1

If all the different types of iVar’s you intend on initializing in the subclasses are descended from a common class, then I’d store that class in the super, or else just store it as an id. Then, setup a property accessor in each of your subclasses the casts the iVar as you need it.

@interface superClass : NSObject{
    id _superIvar;
}
@end

@implementation superClass : NSObject
    ....super's code....
@end

Now in the implementation of the subclass declare a property in a category, shown below (or in the interface, if you want it public)

@interface subClass (private)
@property (strong) ClassType *superIvar;
@end;

@implementation  
- (void) setSuperIvar:(ClassType *)superIvar{
    _superIvar = superIvar;
}
- (ClassType *) superIvar{
    return (ClassType *) _superIvar;
}

- (void) someMethodThatUsesSuperIvar{
    [self.superIvar doSomething];
}
@end

Alternatively, if you don’t want to open your _superIvar to direct access, you can set a property on the superclass and access through the property on the subclass. But in this way you can easily access super’s ivars cast to the appropriate type.