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detect:ifNone:

Learn detect:ifNone: in Smalltalk with a construct-specific explanation, a unique example, a practical boundary, and a mastery check.

10 min read • Intermediate

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

smalltalk-04-09-detect-ifnone.st
smalltalk Try It Live
#(3 5 8 9) detect: [ :n | n even ] ifNone: [ 0 ].
Edge case / engineering note

Change the key input in this Smalltalk example and predict the result first; the named construct should be the reason the behavior changes.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content