Class: VirtualDictionary

• Inheritance
• Description
• Instance protocol
  • accessing
  • initializing
  • testing

Inheritance:

   Object
   |
   +--Collection
      |
      +--VirtualDictionary
         |
         +--VirtualDictionaryWithCache

Package:

stx:libbasic2

Category:

Collections-Unordered

Version:

rev: 1.12 date: 2023/11/15 07:22:18

user: cg

file: VirtualDictionary.st directory: libbasic2

module: stx stc-classLibrary: libbasic2

Description:

a collection which looks like a (usually read-only) dictionary to the outside,
but invokes a pluggable fetchBlock to retrieve keys and optional storeBlock
to change values.
The fetchBlock is called for at:ifAbsent: and is supposed to
return an object for the given argument(key) or nil if there is no such value.
For example,
    VirtualDictionary new fetchBlock:[:key | key squared]
will respond to:
    at:4
with 16.        

VirtualDictionary does not remember previously computed values,
whereas VirtualDictionaryWithCache does.

Caveat:
    a virtual dictionary does not support:
        size
        do:     (and all other enumeration messages)
    actually it does not behave at all like a dictionary.


[instance variables:]

[class variables:]

copyright
COPYRIGHT (c) 2018 by eXept Software AG
             All Rights Reserved

This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice.   This software may not
be provided or otherwise made available to, or used by, any
other person.  No title to or ownership of the software is
hereby transferred.

Instance protocol:

 at: aKey

retrieve a value from this (virtual) dictionary.

 at: aKey ifAbsent: exceptionValue

retrieve a value from this (virtual) dictionary.

 at: aKey put: aValue

store a value in this (virtual) dictionary.
May raise an error, if storing is not allowed or if the key is wrong

 do: aBlock

enumerate the elements (if possible); raise an error if not.

 includesKey: aKey

return true if aKey is in this (virtual) dictionary.

 size

return the size (if known); raise an error if not known.

 checkKeyBlock: aOneArgBlock

define the checkKeyblock; this is invoked with the key to check for presence

 doBlock: aOneArgBlock

define the doblock; this is invoked to enumerate the virtual elements

 fetchBlock: aOneArgBlock

define the fetchblock; this is invoked with the key to fetch

 sizeBlock: aBlock

define the sizeblock; this is invoked to ask for the virtual size

 storeBlock: aTwoArgBlock

define the storeblock; this is invoked with the key and value to store

 isVirtualCollection

(comment from inherited method)
true if this is a collection which generates elements via
some algorithm (such as reading a file).
Some care should be taken then, as not all operations are possible then.

 isVirtualDictionary