| library book1 book2 checkoutAction |
 
book1 := Dictionary new at: #title put: 'BookA'; at: #available put: true; yourself.
book2 := Dictionary new at: #title put: 'BookB'; at: #available put: true; yourself.
 
library := OrderedCollection with: book1 with: book2.
 
checkoutAction := [:aLibrary :aTitle |
    | book |
    book := aLibrary detect: [:b | (b at: #title) = aTitle] ifNone: [nil].
    (book notNil and: [book at: #available])
        ifTrue: [
            book at: #available put: false.
            Transcript show: 'Success: ', aTitle, ' checked out.'; cr.]
        ifFalse: [
            Transcript show: 'Failed: ', aTitle, ' not available.'; cr.]
].
 
checkoutAction value: library value: 'BookA'.
checkoutAction value: library value: 'BookA'.

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