Swift: Edit value of Label when pressing a button - ios

Question

I'm trying to learn Swift and I'm playing around with the basics of variables. I made an app where when you press a button, the value of a label changes, and while the button that adds 1 works, the one that subtracts one doesn't. If I change the first button (plusone) to subtract one, then it works, so I assume it is something to do with how the code is parsed? Would you be kind enough to explain how this works? Thanks in advance.
The code is here:
import UIKit
class ViewController: UIViewController {
var value = 0
#IBOutlet var number: UILabel!
#IBAction func plusone(_ sender: Any) {
value = value+1
number.text = "\(value)"
}
#IBAction func plustwo(_ sender: Any) {
value = value-1
number.text = "\(value)"
}
}
And the app looks like this if that matters:
Screenshot
The second button is named 'plustwo' because I haven't figured out where else I need to rename it, if I just rename it here the app displays a blank screen and nothing else.

Answer 1

From the comments:
I changed plustwo to -2 and it works as intended. Pressing Add One
adds one and pressing Substract One substracts one. I am not sure why.
The behavior you describe tells me that you have your Subtract One button wired to both the plusone and plustwo functions. You can check this by control-clicking on your button in Interface Builder and checking the connections. If you see TouchUpInside wired to two functions, remove one by clicking on the x to delete the connection.
Another way you can verify the behavior is to add logging print statements to your functions such as print("in plusone") and print("in plustwo"). When you press Subtract One, if you see both messages in the console then you know you have your button connected to both #IBActions.
How did this happen? This frequently happens when you copy a button in Interface Builder that already has a connection to an #IBAction. Connecting it to a new #IBAction doesn't replace the first one, it just connects to both of them and calls both when the button is pressed.
The second button is named 'plustwo' because I haven't figured out
where else I need to rename it, if I just rename it here the app
displays a blank screen and nothing else.
To rename the function, you need to change the name of the function and remove and reconnect the connection in Interface Builder. As described above, control-click on the button in Interface Builder and remove the connection to the old function name, then connect the button to the new function.