BrianSlick

Nothing you have shown here is related to Core Data in any way, so that can't be the issue.

For a given property:

@property (strong, nonatomic) IBOutlet UITextField *dollars;

if you are auto-synthesizing them (you are if this is all of your code), the instance variable name corresponding to this property is _dollars.

To use the property:

self.dollars.text = @"Whatever";
NSString *something = self.dollars.text;

To use the instance variable:

_dollars.text = @"Whatever";
NSString *something = _dollars.text;

It's less of an issue with ARC, but generally speaking you want to use the property, not the instance variable.

The auto-generated instance variable name recently changed to include the underscore. And I think that if you manually @synthesize but do not specify a variable name, the underscore will not be there, so dollars.text would work. To summarize:

@property (strong, nonatomic) UITextField *dollars;
....
@synthesize dollars;
// --> instance variable name: dollars

- vs -

@property (strong, nonatomic) UITextField *dollars;
....
// @synthesize dollars; (don't synthesize)
// --> instance variable name: _dollars

- vs -

@property (strong, nonatomic) UITextField *dollars;
....
@synthesize dollars = ivDollars
// --> instance variable name: ivDollars

I'm generally on board with less code being better, so skip synthesizing and get used to the _name convention.

Also, use better variable names. It isn't "dollars", which would suggest a number, it is a text field, so the name should reflect this. "dollarTextField", etc. A good rule of thumb for variable names is (purpose)+(kind of entity).

I think maybe your IBOutlets should be assigned as weak, not strong.
The view will have strong references to your outlets so they never be deallocated from the heap. Assigning them as weak will ensure that when the view disappears, the outlets will get cleared from the heap.

Not quite. Apple's newer code is showing IBOutlets as weak, and I guess this is what has been done on the Mac side for a while, but I strongly disagree with it.

The reason for weak vs strong has to do with what happens when the parent view is removed and can be deallocated. For example using this view controller, when self.view goes away, self.dollars - a subview - would continue to exist in a strong property, but would be cleared out for a weak property. This does not mean you cannot deallocate the text field. You can clear out the property manually at any time, or (with ARC) it will be cleared out in the VC's dealloc method.

I have a philosophical problem with using weak for IBOutlets, that being why would I NOT use strong for something - anything - that I want to keep around? Old school, if I wanted to keep it around, it would be retained, and when I was done with it, it would be released. Just because we're using ARC and strong/weak now doesn't change the premise that something I want should be retained until I want to let it go. By going with weak, the item could go away at a time you don't intend, and I really don't understand letting that happen.

There is an argument to be made that "Well, if self.view is going away, why does your IBOutlet need to stick around instead of also going away?" I suppose, but this argument falls down quickly if you have IBOutlets that are NOT subviews of self.view. I just smacked into this a couple days ago in a project where the style is to use weak. I had a separate view that I wanted to be able to show later, but it was not placed in self.view's hierarchy initially. After the xib was loaded, that property got cleared out, my view disappeared, and then nothing happened when I tried to use it later. Change weak to strong, voilà, everything worked fine. So then you have to keep track of "ok, this IBOutlet is in self.view, so I'll use weak, this one isn't, so I'll use strong, etc." Screw that. Use strong across the board. Clean up manually if needed. The alternative is to throw everything into self.view all at once, but that just renders your xib unreadable to normal humans. Again, screw that.

Come on now.

messageText = [messageText stringByReplacingOccurrencesOfString: @"\n" withString: @""];
messageText = [messageText stringByReplacingOccurrencesOfString: @"\r" withString: @""];

Use the same MainWindow.xib. In code, determine which device you're on, and then set the appropriate view controller to be the root for the window.

You have to declare the method in the .h file of MasterViewController. See sample code at that link.

Yup.