menu_book Course Curriculum (Smalltalk Complete Course) expand_more
detect:ifNone:
Learn detect:ifNone: in Smalltalk with a construct-specific explanation, a unique example, a practical boundary, and a mastery check.
detect:ifNone: is an atomic Smalltalk topic inside Collections. The example below uses the actual construct named by the lesson rather than a generic placeholder.
Focus on what detect:ifNone: changes: the input, binding, control path, object state, collection, runtime effect, or language contract. Then alter one value and verify that the behavior changes for a reason specific to this feature.
Topic-specific example
#(3 5 8 9) detect: [ :n | n even ] ifNone: [ 0 ].
Change the key input in this Smalltalk example and predict the result first; the named construct should be the reason the behavior changes.