iOS UILabel on new View Controller not updating when using segue - ios

Question

I have a UILabel(descriptionOfProgram) on a second ViewController(GraphViewController) that needs to be set when the segue from the original MVC occurs.
Currently, in my main MVC, I do two things in my prepareForSegue::
I set an #property NSString in GraphVewController to the string I want it to be.
I set descriptionOfProgram's text to be equal to that string by calling a function in GraphViewController setDescriptionLabel:.
When graphViewController comes on string, the text is not in the label. During testing, I created a button called test in GraphViewController to call setDescriptionLabel when pressed. This worked. Any ideas on what's going on?
I included GraphViewController.h and .m in the second MVC, and GraphingCalculatorViewController.m in the Main MVC.
GraphViewController.h:
//
// GraphViewController.h
// GraphingCalculator
//
// Created by Graham Gaylor on 3/1/12.
// Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//
#import <UIKit/UIKit.h>
#interface GraphViewController : UIViewController
#property (nonatomic,copy) NSArray *program;
#property (nonatomic,weak) NSString *description;
#property (weak, nonatomic) IBOutlet UILabel *descriptionOfProgram;
- (IBAction)test:(id)sender;
- (void)setDescriptionLabel:(NSString *)description;
#end
GraphViewController.m:
//
// GraphViewController.m
// GraphingCalculator
//
// Created by Graham Gaylor on 3/1/12.
// Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//
#import "GraphViewController.h"
#import "GraphView.h"
#interface GraphViewController() <GraphViewDataSource>
#property (nonatomic, weak) IBOutlet GraphView *graphView;
#end
#implementation GraphViewController
#synthesize program = _program;
#synthesize descriptionOfProgram = _descriptionOfProgram;
#synthesize description = _description;
#synthesize graphView = _graphView;
- (void)setProgram:(NSArray *)program
{
_program = program;
[self.graphView setNeedsDisplay]; // any time our Model changes, redraw our View
self.graphView.dataSource = self; // setting graphView delegate GraphVC
}
- (IBAction)test:(id)sender {
self.descriptionOfProgram.text = #"test";
[self setDescriptionLabel:self.description];
}
- (void)setDescriptionLabel:(NSString *)description
{
NSLog(#"Got into setDescriptionLabel");
self.descriptionOfProgram.text = #"hello";
}
- (NSArray *)programForGraphView:(GraphView *)sender {
return self.program;
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return YES;
}
- (void)viewDidUnload {
[self setDescriptionOfProgram:nil];
[super viewDidUnload];
}
#end
This is my main MVC. I got rid of all the extra functions that don't deal with the seque.
GraphingCalculatorViewController.m:
//
// GraphingCalculatorViewController.m
// GraphingCalculator
//
// Created by Graham Gaylor on 3/1/12.
// Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//
#import "GraphingCalculatorViewController.h"
#import "GraphViewController.h"
#interface GraphingCalculatorViewController()
#property (nonatomic,strong) NSArray *programToGraph;
#end
#implementation GraphingCalculatorViewController
#synthesize programToGraph = _programToGraph;
- (void)setAndShowGraph:(NSArray *)program {
self.programToGraph = program;
[self performSegueWithIdentifier:#"ShowGraph" sender:self];
NSLog(#"setAndShowGraph");
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if([segue.identifier isEqualToString:#"ShowGraph"]) {
[segue.destinationViewController setProgram:self.programToGraph]; // sets GraphVC's program to current program
[segue.destinationViewController setDescriptionLabel:[CalculatorBrain descriptionOfProgram:self.programToGraph]];
NSLog(#"prepareForSegue");
}
}
- (IBAction)graphPressed {
[self setAndShowGraph:self.brain.program];
}
- (void)viewDidUnload {
[self setVariablesUsed:nil];
[super viewDidUnload];
}
#end

Answer 1

prepareForSegue: is called before viewDidLoad: so your IBOutlet will be nil. Try setting the incoming value to a NSString and then use that string to populate the label on viewDidLoad: