Error? Reading variable inside IBAction Button

Question

I have an IBAction that needs to read from a variable. However, when placing the variable outside of the viewDidLoad I receive the error

Cannot use instance member 'animal' within property initializer; property initializers run before 'self' is available

My code is as follows. When I move the variable back inside the viewDidLoad the error states that animalName is undeclared

var animalName = (String(format: "%03d", animal.speciesId!))

@IBAction func megaKeyIBO(_ sender: Any) {
    animalName = (String(format: "%03d", animal.speciesId!)) + "-merg"
}

override func viewDidLoad() {
    super.viewDidLoad()

    //variable was originally here before moving to top
    var animalName = (String(format: "%03d", animal.speciesId!))
}

Answer 1

This happens because you're trying to initialize your animalName before your property animal.speciesId! has been initialized. A simply way to solve would be this:

var animalName: String!

@IBAction func megaKeyIBO(_ sender: Any) {
    animalName = (String(format: "%03d", animal.speciesId!)) + "-merg"
}

override func viewDidLoad() {
    super.viewDidLoad()

    // Initialize on viewDidLoad
    animalName = (String(format: "%03d", animal.speciesId!))
}

Answer 2

You are using the variable animalName as a local variable when you declare it in viewDidLoad()

Local variables only work in the functions they are declared in order to use animalName in the button you created it must be declared as an instance variable or in the function for the button