How to subclass UIButton to allow to copy and encode for archiving?

Question

I have an app where I need to track the last button pressed at all times. So I have implemented this method:

-(void) lastButtonPressed: (id)sender
{
    lastButtonPressed = (UIButton *)sender;
}

Then when any button gets pressed I call:

[self lastButtonPressed = xButton];

Works perfect. But now I am working on archiving all of the objects in my app when the view disappears or closes to then unarchive it and UIButton doesn't conform to NSCopying or NSCoding. I have read that I can subclass UIButton and define the methods but I am stuck there.

So when my app closes or the view disappears I want to save the lastButtonPressed.

I created a new class called BIDPersistence to hold my archived data. In my app's view controller I have a saveData method where I save my data. I get an error on the last line shown below because UIButton doesn't conform.

BIDPersistence *persistence = [[BIDPersistence alloc] init];
    persistence.field1 = [NSNumber numberWithDouble:double1];
    persistence.field2 = [NSNumber numberWithDouble:double2];
    persistence.field3 = display.text;
    persistence.field4 = tapeDisplay.text;
    persistence.field5 = [NSNumber numberWithBool:continueTape];
    persistence.field6 = [NSNumber numberWithBool:newDouble];
    persistence.field7 = lastButtonPressed;

Any help appreciated.

Answer 1

It sounds like you don't have to save the actual button, just know which one was pressed last. For this you could use NSUserDefaults, which is good for saving little tidbits without having to set up Core Data or the like. What I would recommend is to give each button a unique tag (in interface builder, just an int) then do this:

[[NSUserDefaults standardUserDefaults] setInt:[lastButton tag] forKey:@"LastButtonPressed"];

later you can retrieve the button by using viewWithTag:.

Answer 2

You can't really subclass UIButton. It's not a single class but, as they say, a class cluster that UIKit selects based on UIButton's + (id)buttonWithType:(UIButtonType)buttonType.

That said, it does (appear) to conform to NSCoding (just reading the docs; I don't know how the NSCoding stuff works.)