Why am I getting nil for this string value? - swift

Question

Basically I'm trying to make a simple note app, and here I'm just trying to display the title and content.
Project (note) file
import Foundation
class Project
{
var title = " "
var content = " "
var after = " "
}
Note detail view controller file
class NoteDetailViewController: UIViewController
{
var project: Project!
#IBOutlet weak var titleTextField: UITextField!
#IBOutlet weak var contentTextField: UITextView!
#IBOutlet weak var afterTextField: UITextView!
override func viewWillAppear(animated: Bool)
{
super.viewWillAppear(animated)
titleTextField.text = project.title
contentTextField.text = project.content
afterTextField.text = project.after
contentTextField.sizeToFit()
afterTextField.sizeToFit()
}
override func viewWillDisappear(animated: Bool)
{
super.viewWillDisappear(animated)
project.title = titleTextField.text!
project.content = contentTextField.text!
}
}
When I reference any of the project. files, I get nil. I have no idea why I'm getting nil from a string?

Answer 1

You need to initialize the class "Project" correctly.
let project = Project()

Answer 2

It seems to me project is not initialized;
project = new Project()
so accessing its properties will eventually return nil because the object does not exist

Answer 3

Yes, initializing the property definitely fixes the issue but there's a reason behind the error being thrown, and its one that's worth understanding rather than just initializing the property to make the error go away.
When you declare your property as:
var project: Project! //- with a !
You are declaring an optional property that immediately gets unwrapped (Implicit Unwrapping), this means that the compiler expects you to handle the case where the property is nil, and it wont throw compile errors when you use the property (as it has already been unwrapped). Which is not ideal as Swift is designed to try to catch as many errors at compile time, rather than at run time, and by unwrapping your optional when you declare it you are missing out on all that goodness.
In your every day swift you would declare optional properties as so:
var project: Project?
Which would throw a compile time error if you try to access the property value without unwrapping it. For example when doing:
var project: Project?
override func viewWillAppear(animated: Bool)
{
super.viewWillAppear(animated)
titleTextField.text = project.title //- The compiler will scream at you here.
contentTextField.text = project.content
afterTextField.text = project.after
contentTextField.sizeToFit()
afterTextField.sizeToFit()
}
If you you don't need your property to be an optional, initialize the variable when you declare it, or do so in the constructor of your class (where it applies), and avoid Implicitly unwrapping your optionals as this can have the potential of resulting in run time errors.
Hope this helps!