Switching in F-Script

There is no switch/case statement or method in F-Script and Smalltalk. Usually, switching is done by taking advantage of object polymorphism or by simply nesting ifTrue:IfFalse: messages. For example, here is some C pseudo code with a switch statement:

switch (aValue)
{
    case 1: doSomething1;
            break;   
    case 2: doSomething2;   
            break;
    case 3: doSomething3;   
            break;
}     

We can write equivalent code in F-Script using ifTrue:IfFalse: messages:

aValue = 1 ifTrue:[doSomething1] ifFalse:[
aValue = 2 ifTrue:[doSomething2] ifFalse:[
aValue = 3 ifTrue:[doSomething3]]]

Another possible technique is based on blocks and dictionary lookup. Basically, we construct a dictionary whose keys are the various cases’ values we want to check against and whose values are blocks of code to execute. We then do a lookup in the dictionary and execute the selected block. With our example, this gives:

cases := #{
  1 -> [doSomething1],
  2 -> [doSomething2],
  3 -> [doSomething3]
}.
(cases objectForKey:aValue) value

Searching for Smalltalk switch case on the Web will get you to additional techniques and discussions on emulating switch statements.

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