Delegates: Difference between revisions
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(added ruby) |
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| Line 381: | Line 381: | ||
self.delegate = None |
self.delegate = None |
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def operation(self): |
def operation(self): |
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if hasattr(self.delegate, 'thing'): |
if hasattr(self.delegate, 'thing') and callable(self.delegate.thing): |
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return self.delegate.thing() |
return self.delegate.thing() |
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return 'default implementation' |
return 'default implementation' |
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| Line 402: | Line 402: | ||
a.delegate = Delegate() |
a.delegate = Delegate() |
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assert a.operation() == 'delegate implementation'</lang> |
assert a.operation() == 'delegate implementation'</lang> |
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=={{header|Ruby}}== |
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<lang ruby>class Delegator |
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def initialize |
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@delegate = nil |
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end |
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def delegate |
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@delegate |
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end |
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def delegate=(x) |
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@delegate = x |
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end |
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def operation |
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if @delegate.respond_to?(:thing) |
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@delegate.thing |
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else |
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'default implementation' |
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end |
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end |
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end |
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class Delegate |
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def thing |
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'delegate implementation' |
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end |
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end |
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if __FILE__ == $PROGRAM_NAME |
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# No delegate |
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a = Delegator.new |
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puts a.operation # prints "default implementation" |
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# With a delegate that does not implement "thing" |
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a.delegate = 'A delegate may be any object' |
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puts a.operation # prints "default implementation" |
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# With delegate that implements "thing" |
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a.delegate = Delegate.new |
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puts a.operation # prints "delegate implementation" |
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end</lang> |
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=={{header|Tcl}}== |
=={{header|Tcl}}== |
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