Code encapsulation using closures
Swift’s closures are awesome - and super handy when it comes to encapsulating code - especially in init methods. You usually want to keep your init methods short & sweet, and in Objective-C many developers accomplish this by delegating setup to separate methods. Like this pattern:
MyClass {
init() {
self.setupView()
self.setupObservers()
}
func setupView() {
...
}
func setupObservers() {
...
}
}
This doesn’t work very well in Swift, considering that you want to use constants (let) as much as possible, and you cannot call methods on an object that hasn’t been fully initialized yet. So, I’ve started using closures for this. Say you have a closure called Calculate, like this one:
func Calculate<T>(closure: () -> T) -> T {
return closure()
}
This allows you to encapsulate your code, without creating tons of utility methods, and still keeping all your setup code in your init method, like this:
MyClass {
let view: UIView
let observers: [Observer]
init() {
self.view = Calculate {
var frame = CGRect()
frame.size.origin = 100
frame.size.width = 300
return UIView(frame: frame)
}
self.observers = Calculate {
var observers = [Observer]()
observers.append(OrdinaryObserver())
if someCondition {
observers.append(SpecialObserver())
}
return observers
}
}
}