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  1. "the original definition of class Price"
  2.  
  3. Object subclass: Price [
  4.    | value |
  5.    init [ value := 0 ]
  6.    value [ ^value ]
  7.    value: newValue [ value := newValue ]
  8. ]
  9.  
  10. Price class extend [
  11.    new [ ^ super new init; yourself ]
  12.    value: value [ ^self new value: value; yourself ]
  13. ]
  14.  
  15.  
  16. "tweaks for accepting decorations"
  17.  
  18. Price extend [
  19.    | decorators |
  20.    decorators [ ^decorators ifNil: [ decorators := OrderedCollection new ] ]
  21.    value [ ^self decorators inject: value into: [ :acc :deco | deco value: acc ] ]
  22. ]
  23.  
  24.  
  25. "usage example"
  26.  
  27. | price |
  28. price := Price value: 120.
  29. price decorators
  30.    add: [:x | x * 2]; 
  31.    add: [:x | x + 80]; 
  32.    add: [:x | x * 2]; 
  33.    add: [:x | x + 200].
  34. price value displayNl
Success #stdin #stdout 0.01s 335424KB
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https://ideone.com/d8iLSE
language:
Smalltalk (gst 3.2.5)
created:
7 years ago
visibility:
public

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