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Delegates: Difference between revisions
→{{header|Swift}}
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=={{header|Swift}}==
Allowing the delegate to be any type and taking advantage of dynamism of method lookup:
<lang swift>import Foundation
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weak var delegate: AnyObject?
func operation() -> String {
if let
return
} else {
return "default implementation"
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// With a delegate that implements "thing":
let d = Delegate()
a.delegate = d
println(a.operation()) // prints "delegate implementation"</lang>
Alternately, requiring the delegate to conform to a given protocol:
<lang swift>protocol Thingable : class {
func thing() -> String
}
class Delegator {
weak var delegate: Thingable?
func operation() -> String {
if let d = self.delegate {
return d.thing()
} else {
return "default implementation"
}
}
}
class Delegate : Thingable {
func thing() -> String { return "delegate implementation" }
}
// Without a delegate:
let a = Delegator()
println(a.operation()) // prints "default implementation"
// With a delegate:
let d = Delegate()
a.delegate = d
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