"{ Encoding: utf8 }"

"{ Package: 'stx:libbasic2' }"

"{ NameSpace: Smalltalk }"

Collection subclass:#VirtualDictionary

	instanceVariableNames:'fetchBlock'

	classVariableNames:''

	poolDictionaries:''

	category:'Collections-Unordered'

!

!VirtualDictionary class methodsFor:'documentation'!

documentation

"

    a collection which looks like a (read-only) dictionary to the outside,

    but invokes a pluggable fetchBlock to retrieve keys.

    [author:]

        cg

    [instance variables:]

    [class variables:]

    [see also:]

"

! !

!VirtualDictionary methodsFor:'accessing'!

at:aKey

    ^ self at:aKey ifAbsent:nil

!

at:aKey ifAbsent:exceptionValue

    |value|

    value := fetchBlock value:aKey.

    value isNil ifTrue:[

        ^ exceptionValue value

    ].

    ^ value

!

fetchBlock:something

    fetchBlock := something.

! !

!VirtualDictionary methodsFor:'queries'!

includesKey:aKey

    ^ (fetchBlock value:aKey) notNil

! !

!VirtualDictionary class methodsFor:'documentation'!

version

    ^ '$Header$'

!

version_CVS

    ^ '$Header$'

! !