Question

I am working on a delegate class that controls several views, and find myself switching between updating properties in the delegate and returning values from methods. What is the proper way to do this?

-(NSArray)blah{
return myarray;
}

or
-(void)blah{
[self myarray:value]
}

————— Clarification of question below

if I have a helper method that converts an NSArray into a NSDictionary
should I call my helper method and expect a return of NSDictionary, or should I update a variable in memory and return void.

Answer 1

There’s a case for each approach, depending on what you are really doing. The two choices are:

• It is truly a helper method, that has use in many places in your application.
• It is specific to a single class and the dictionary is a member of that class.

OPTION 1) If it is truly a helper method, I believe that you should return the NSDictionary from the method. I’m assuming it is newly allocated within that method.

In other words, prefer:

+ (NSDictionary *) dictFromArray:(NSArray *);

If it has utility outside of a single class, you could put it in a sensible class that collects related utility methods.

The alternative approach of passing in an empty dictionary to be filled is practiced in C because it creates symmetry around allocating and freeing and makes it clear who owns the memory.

In Objective-C, reference counting takes care of that, so you can avoid the extra code of allocating empty objects just to call the method.

For example:

NSMutableDictionary *myDict = [[NSMutableDictionary alloc] init];
dictFromArray(myArray, myDict);

When it comes to knowing who owns the object, you should stick to Objective-C conventions, where:

+ (NSDictionary *) dictFromArray:(NSArray *)array

returns an autorelease object, so the caller knows they need to retain it if they want to hold a reference.

OPTION 2) If the functionality is specific to a single class and that class has the dictionary as a member, then I would pass in the array, update the dictionary member variable using the array contents, and return void.

Something like:

- (void) setBlahFromArray:(NSArray *)array