Program a UIButton to change UILabel - objective-c

Question

I am trying to use Objective-C in iOS Single View app to program a UIButton to change the text in a UILabel. Is there a way to run a function for this to be implemented in my "ViewController.m" file?
Here is my Source Code:
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)loadView {
//UIBUTTON
//allocate the view
self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
//set the view's background color
self.view.backgroundColor = [UIColor whiteColor];
//create the button
UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
//set the position of the button
button.frame = CGRectMake(50, 280, 280, 50);
//set the font size of the button
button.titleLabel.font = [UIFont systemFontOfSize:40];
//set the text color of the button, before it is pressed
[button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
//set the text color of the button, while it is pressed
[button setTitleColor:[UIColor grayColor] forState:UIControlStateHighlighted];
//set the button's title
[button setTitle:#"3" forState:UIControlStateNormal];
//listen for clicks
[button addTarget:self action:#selector(buttonPressed)
forControlEvents:UIControlEventTouchUpInside];
//add the button to the view
[self.view addSubview:button];
//UILABEL
UILabel *Question=[ [UILabel alloc] initWithFrame:CGRectMake(10,200,350,60)];
Question.text=#"How many horns does a Triceratops have?";
Question.backgroundColor = [UIColor grayColor];
Question.textColor = [UIColor whiteColor];
Question.font=[UIFont fontWithName:#"Helvetica" size:18 ];
[self.view addSubview:Question];
}
-(void)buttonPressed { }
#end
Is it possible to trigger the change in text in my buttonPressed function? Thanks so much for anybody's help!

Answer 1

The problem is that when you create your label and add it to the interface...
UILabel *Question=[ [UILabel alloc] initWithFrame:CGRectMake(10,200,350,60)];
// ...
[self.view addSubview:Question];
...you didn't keep a reference to it. So now, in buttonPressed, you have no way to talk about the label.
Make a property:
#interface ViewController ()
#property (nonatomic, weak) UILabel* questionLabel;
#end
... and when you create the label, remember to set that property to that label. Now you will be able to access the text of that label later on, in buttonPressed (or anywhere else), through the property.