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