IOS making buttons to work between viewcontrollers - ios

Question

I asked a question similiar to this before and got many answers first of all thanks for them but because of the complexity of the project I didnt understand the answer so I decided to ask it again this time in a very simple form.
I have one button in viewcontrollerA and I want that button to write on a Label which is in viewcontrollerB.Its simple a button at A will set the Label text on B.
Example
User opens the app
Clicks the button at page A
Second Page comes up and in that page label text is set by the label.text code came from viewcontroller A it calls the code
Or maybe I can call the code of A from B its not important as long as I make it.I can make butons to open another viewcontrolers so you dont need to explain it.
Also if any other ways around and as long as they are simple I can do them too.Maybe I wrote the code elsewhere and call it from A and B.
Please explain it step by stem cause I have little knowlage about objective C and xcode.
I ask this question to learn about connections between viewcontrollers.In reality I will make that button to display a random number at the second page but its not important rightnow cause if I learn to make simple connection I can do the rest.

Answer 1

In your action, you need to have a reference to the second view controller. For example
- (IBAction)buttonAClicked:(id)sender {
ViewController2 *vc2 = [[ViewController2 alloc] initWithNibName:#"ViewController2" bundle:nil];
[self.navigationController pushViewController:vc2 animated:YES];
vc2.someVariable = #"This is random text";
[vc2.someButton setTitle:#"Some button text" forControlState:UIControlStateNormal];
}
This shows how you would create a second view controller, change two properties, and then push it.

Answer 2

In your second view controller create a property called theText that is an NSString and then in the viewDidLoad assign the label.text to the NSString;
- (void)viewDidLoad
{
if(self.theText)
self.label.text = self.theText;
}
Now use your first view controller to set theText in the second view controller.
If you are using a segue use prepareForSegue:
- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([[segue identifier] isEqualToString:#"Second View Segue"])
{
SecondViewController *theController = segue.destinationViewController;
theController.theText = #"Some text";
}
}
If you are using some sort of modal presentation:
SecondViewController *theController = [[SecondViewController alloc] init];
theController.theText = #"Some text";
[self presentModalViewController:theController animated:YES];
or if you are using a navigation controller:
SecondViewController *theController = [[SecondViewController alloc] init];
theController.theText = #"Some text";
[self.navigationController pushViewController:theController animated:YES];
So your first view controller will set the NSString property in the second, then the second will set the UILabel equal to the NSString during it's load. You can not set the text of a UILabel before the second view controller is loaded, so something like:
SecondViewController *theController = [[SecondViewController alloc] init];
theController.label.text = #"Some text";
[self.navigationController pushViewController:theController animated:YES];
will not work correctly, because you can't set the text for the label until the view is loaded.
Hope that helps.