Apple's docs specify that:
willSet and didSet observers are not called when a property is first initialized. They are only called when the property’s value is set outside of an initialization context.
Is it possible to force these to be called during initialization?
Let's say I have this class
class SomeClass {
var someProperty: AnyObject {
didSet {
doStuff()
}
}
init(someProperty: AnyObject) {
self.someProperty = someProperty
doStuff()
}
func doStuff() {
// do stuff now that someProperty is set
}
}
I created the method doStuff
, to make the processing calls more concise, but I'd rather just process the property within the didSet
function. Is there a way to force this to call during initialization?
I decided to just remove the convenience intializer for my class and force you to set the property after initialization. This allows me to know didSet
will always be called. I haven't decided if this is better overall, but it suits my situation well.
If you use defer
inside of an initializer, for updating any optional properties or further updating non-optional properties that you've already initialized and after you've called any super.init()
methods, then your willSet
, didSet
, etc. will be called. I find this to be more convenient than implementing separate methods that you have to keep track of calling in the right places.
For example:
public class MyNewType: NSObject {
public var myRequiredField:Int
public var myOptionalField:Float? {
willSet {
if let newValue = newValue {
print("I'm going to change to \(newValue)")
}
}
didSet {
if let myOptionalField = self.myOptionalField {
print("Now I'm \(myOptionalField)")
}
}
}
override public init() {
self.myRequiredField = 1
super.init()
// Non-defered
self.myOptionalField = 6.28
// Defered
defer {
self.myOptionalField = 3.14
}
}
}
Will yield:
I'm going to change to 3.14
Now I'm 3.14