Prevent duplicate printout of element in NSMutableArray - objective-c

Question

I am using a singleton class to transfer a NSMutableArray across views.
The issue I am having is my array is getting displayed multiple times.
Right now I am working with three UITextFields. Each is getting added to the array and outputted in a specific format. Here is what my output looks like:
A / B
C
A / B
C
A / B
C
All I need shown is:
A / B
C
Here is my code if someone can help me find what is missing or needs to be reworked:
To display the text:
UILabel * myLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 10, 300, 200)];
[myLabel setFont:[UIFont fontWithName:#"Helvetica" size:10.0]];
myLabel.numberOfLines = 0;
NSMutableString * string = [NSMutableString string];
Education * myEducation = [Education sharedEducation];
for (Education * output in myEducation.educationOutputArray)
{
[string appendString:[NSString stringWithFormat:#"%# / %# \n%#\n", [myEducation.educationOutputArray objectAtIndex:0], [myEducation.educationOutputArray objectAtIndex:1], [myEducation.educationOutputArray objectAtIndex:2], nil]];
}
myLabel.text = string;
[self.view addSubview:myLabel];
Here is where I am saving the text:
-(void)saveButtonTapped:(id)sender
{
[_educationArray addObject:_aTextField.text];
[_educationArray addObject:_bTextField.text];
[_educationArray addObject:_cTextField.text];
Education * myEducation = [Education sharedEducation];
myEducation.educationOutputArray = _educationArray;
[self.navigationController popViewControllerAnimated:YES];
}
EDIT *
When a user is entering text into the text fields they can also add a new set of text using the same three text fields.
If I removed the for loop only the first is displayed. How can I get all of the text to display?
EDIT TWO *
I tried this:
[string appendString:[NSString stringWithFormat:#"%# / %# \n%#\n", [output major], [output university], [output timeAtSchool]]];
Results in this error:
2012-12-29 17:03:07.928 EasyTable[14501:c07] -[__NSCFString major]: unrecognized selector sent to instance 0x7176850
2012-12-29 17:03:07.941 EasyTable[14501:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString major]: unrecognized selector sent to instance 0x7176850'
*** First throw call stack:
(0x1c99012 0x10d6e7e 0x1d244bd 0x1c88bbc 0x1c8894e 0x6162 0xff817 0xff882 0xffb2a 0x116ef5 0x116fdb 0x117286 0x117381 0x117eab 0x1184a3 0x118098 0x2c10 0x10ea705 0x21920 0x218b8 0xe2671 0xe2bcf 0xe1d38 0x2e5213 0x1c61afe 0x1c61a3d 0x1c3f7c2 0x1c3ef44 0x1c3ee1b 0x1bf37e3 0x1bf3668 0x1e65c 0x240d 0x2335 0x1)
libc++abi.dylib: terminate called throwing an exception

Answer 1

You add three elements at a time to the array, and later you want to process them three at a time.
It would probably be better to create a container class that holds the three elements, and add instances of the container class to the array.
But if you really want to do it this way, you can't use a for/in loop. You have to use an index variable:
NSArray *array = myEducation.educationOutputArray;
for (NSUInteger i = 0, count = array.count; i < count; i += 3) {
[string appendFormat:#"%# / %#\n%#\n", array[i], array[i+1], array[i+2]];
}

Answer 2

you don't have duplicates in the array: the problem is in the for loop
for (Education * output in myEducation.educationOutputArray)
{
[string appendString:[NSString stringWithFormat:#"%# / %# \n%#\n", [myEducation.educationOutputArray objectAtIndex:0], [myEducation.educationOutputArray objectAtIndex:1], [myEducation.educationOutputArray objectAtIndex:2], nil]];
}
here you are looping through the array 3 times (because there are 3 objects in the array) and then printing each object each time. I think you should just do the appendString: line wihtout the for loop

Answer 3

Your for loop is really odd; You loop through each object in the array but then you hardcoded the indexes inside the for loop. I'm not sure what's going on there but it's certainly the source of the odd output. That pointer to an Education object is what you should access. Each time through the loop, use the value of output.
If you're also having uniqueness issues, consider using an NSSet instead of an NSMutableArray. If you care about order, use NSOrderedSet. Set collection types do not allow duplicated values.
Also one more point: If you know you're only going to ever access the values at index 0, 1, and 2, there's really no point to having an NSArray. Just store each value separately and access it directly. At the very least there's no reason for the for loop.
Edit:
You're crashing because you think your array has Education objects in it but it really has plain strings:
-[__NSCFString major]: unrecognized selector sent to instance 0x7176850
Notice that it's saying that you tried to call the method major on an __NSCFString (a private subclass of NSString that apple uses internally). This is a good indicator that your array doesn't contain what you think it does. Make sure you're loading your data into your array correctly by constructing Education objects with the three pieces of data.
You also suggested that you tried
[string appendString:[NSString stringWithFormat:#"%# / %# \n%#\n", output]];
Basically what stringWithFormat: does is take that format string and use it like a template and then it takes as many arguments as you need to fill up the placeholders in the template. %# is a placeholder for an object's description so stringWithFormat: is going to expect three parameters after the format string to fill each %#.