Initializing Swift Variables

Question

I have a question about initializing variables in swift.

I have two ways to initialize a variable (as a "property" of a class in Objective-C).

Which one is the most correct?

class Class {

  var label: UILabel!

  init() { ... label = UILabel() ... }

}

or

class Class {

  var label = UILabel()

  init() { … }

}

Answer 1

In fact, you have 5 ways to initialize properties.

There is no right way, the way depends on needs.
Basically declare objects of type UILabelalways - if possible - as constants ( let).

5 ways:

• Initialization in the ad line

  let label = UILabel(frame:...
  

• Initializing in a method init, you do not need to declare the property as an implicit unwrapped optional.

  let label: UILabel
  init() { ... label = UILabel(frame:...) ... }
  

.

• , viewDidLoad, ( ) , var

  var label: UILabel!
  
  on viewDidLoad()
   ...
   label = UILabel(frame:...)
  }
  

• (). , , .

  let label: UILabel = {
     let lbl = UILabel(frame:...)
     lbl.text = "Foo"
     return lbl
  }()
  

• . ( ), , .
  var

  let labelText = "Bar"
  
  lazy var label: UILabel = {
     let lbl = UILabel(frame:...)
     lbl.text = "Foo" + self.labelText
     return lbl
  }()
  

Answer 2

, init(). , target barButton , self .

class Foo {
    var barButton = UIBarButtonItem(title: "add", style: .Plain, target: self, action: #selector(self.someMethod))

    init(){
        //init here
    }
}

:

class Foo {
    var barButton : UIBarButton? 

    init(){
        barButton = UIBarButtonItem(title: "add", style: .Plain, target: self, action: #selector(self.someMethod))
    }
}

, , , . Apple

Answer 3

 var label: UILabel! 

, nil

var label = UILabel()

. . .

...

var: UILabel! var label = UILabel()?