Refactoring if-chains in Smalltalk without class explosion

Question

As Smalltalk discourages the use of caseOf:, what aternatives exists to implement the following situation without class explosion?

self condition1
        ifTrue: [ self actionForCondition1 ]
        ifFalse: [ 
            self condition2
                ifTrue: [ self actionForCondition2 ]
                ifFalse: [ 
                    self condition3
                        ifTrue: [ self actionForCondition3 ]
                        ifFalse: [ ....  ] ] ]

Answer 1

Depends on how your conditions exactly look like?

• If your conditions are type tests

  anObject isKindOf: aClass
  

  you can dispatch on the class instead, that means you call an action method on anObject.

• If your conditions are equality tests

  anObject = anotherObject
  

  you can use a dictionary with the object as key and the action as a block closure.

• As a last restort and if nothing else helps you might want to rewrite the proposed code to avoid unnecessary nesting:

  self condition1
      ifTrue: [ ^ self actionForCondition1 ].
  self condition2
      ifTrue: [ ^ self actionForCondition2 ].
  self condition3
      ifTrue: [ ^ self actionForCondition3 ].
  ...