How to properly return a value from a method and have it available immediately after application loads?

Question

Hello everyone, first post here so sorry for the length of it. I've been lurking and learning a lot so far but now I have to step in and ask a question. I have read numerous posts here as advised in the FAQs, but I couldn’t find exactly the answer I’m looking for.

Before anything else, let me just say that I'm a total beginner in programming (let alone Objective-C) so please excuse me for any misuse of the terminology. Same goes for any funny english as english not my native language.

I'm building an unit conversion application with a main window containing (among other stuff) two popUpButtons. I'm using indexOfSelectedItem from both popUpButtons in order to calculate a float value (I'm getting the indexes initially in the AwakeFromNib and later in the pop up buttons controller method, when the user change selection).

My problem consists of two parts: first, the code for calculation of that float is pretty massive as I'm comparing every combination of the two indexes of selected items. And second, I would need to have the calculated float value available immediately after launch as the user might want to perform a conversion before using any of the window popUpButtons (otherwise I would put the calculation code in a -(IBAction) method).

So, I'm trying with the following code for calculation of the float value:

@interface MyClass: NSObject

float calculatedFloat;

-(void)setCalculatedFloat:(float)calcFl;
-(float)calculatedFloat;

@implementation MyClass

-(void)setCalculatedFloat:(float)calcFl {
  calcFl = 1.0; // I'm simplifying, this is where I'd like to perform calculation
}

-(float)calculatedFloat {
  return calculatedFloat;
}

Now, for the first part of my problem, when I use the calculatedFloat in another method, say:

-(void)printIt {
  NSLog(@"Calculated float equals: %.2f", calulatedFloat); 
}

all I receive in Debugger is 0.00.

First question would be: if this is not working, how do I properly access this value from within another method?

For the second part of the problem, I'm using -(void)AwakeFromNib; to set up popUpButtons etc. right after the launch but I really wouldn't like to put all of the float calculation code in it only to repeat it somewhere else later.

So the second question would be: is this even possible what I'm trying to achieve? Further more, do I need to move this calculation code to another class? If so, how can I make that other class aware of the indexOfSelectedItem from a popUpButton?

Sorry for the lengthy post and possibly confusing and silly questions. I hope you didn't have to cringe your teeth too much while reading! :)

Thanks!

Answer 1

-(void)setCalculatedFloat:(float)calcFl {
    calcFl = 1.0; // I'm simplifying, this is where I'd like to perform calculation
}

This doesn't show up when you print it later because you assigned to the variable holding the new value, not the variable for the value of the property. You need to assign to your calulatedFloat instance variable. (You typo'ed that variable name, BTW.)

You should move the calculating into another method, and send yourself that message from awakeFromNib and from anywhere that needs to cause recalculation. That method should call setCalculatedFloat: with the calculated value—i.e., setCalculatedFloat: should be just a simple setter. Once you make that change, you could replace your custom accessors with a @synthesize statement and let the compiler write the accessors for you.

My problem consists of two parts: first, the code for calculation of that float is pretty massive as I'm comparing every combination of the two indexes of selected items.

You might see whether you can create custom objects to set as the menu items' representedObject properties, in order to cut out this massive comparison tree. It's hard to be more specific about this without knowing what your comparison tree does.