Editing Conditional (computer programming) (section)

=== Object-oriented implementation in Smalltalk ===

In contrast to other languages, in [[Smalltalk]] the conditional statement is not a [[language construct]] but defined in the class <code>Boolean</code> as an abstract method that takes two parameters, both [[Closure (computer science)|closure]]s. <code>Boolean</code> has two subclasses, <code>True</code> and <code>False</code>, which both define the method, <code>True</code> executing the first closure only, <code>False</code> executing the second closure only.<ref name="Smalltalk conditionals">{{cite web |url = http://wiki.cs.uiuc.edu/VisualWorks/Conditional+Processing |title = VisualWorks: Conditional Processing |date = 2006-12-16 |access-date = 2007-09-09 |archive-url = https://web.archive.org/web/20071022201949/http://wiki.cs.uiuc.edu/VisualWorks/Conditional+Processing |archive-date = 2007-10-22 |url-status = dead }}</ref>

<syntaxhighlight lang="smalltalk">
var = condition 
    ifTrue: [ 'foo' ]
    ifFalse: [ 'bar' ]
</syntaxhighlight>