Class: Visitor

• Inheritance
• Description
• Related information
• Instance protocol
  • helpers
  • subclass responsibility
  • visiting smalltalk types

Inheritance:

   Object
   |
   +--Visitor
      |
      +--AspectVisitor

Package:

stx:libbasic

Category:

System-Visiting

Version:

rev: 1.6 date: 2009/06/08 16:35:38

user: stefan

file: Visitor.st directory: libbasic

module: stx stc-classLibrary: libbasic

Author:

Stefan Vogel (stefan@zwerg)

Description:

This class is abstract and implements the visitor pattern.
It defines #visitXXX:with: messages for various kinds of objects.
Any of these messsages is eventually mapped to #visitObject:with:.

When a class redefines #acceptVisitor:with:, an method has to be defined here, too.

Subclasses have to define at least #visitObject:with:

Related information:

    [bject>>acceptVisitor]

Instance protocol:

 doesNotUnderstand: aMessage

catch unimplemented #visitXXX:with: messages and redirect them to #visitObject:with:.
maybe someone implemented an #acceptVisitor:with: in the XXX class and didn't
implement the corresponding method here.

This should not happen, and a error message is printed, because this can also
occur due to a typo.

 visitChildrenOf: anObject

recursively enumerate anObjects refs, visiting each of the child objects.
nil childs are not visited

 nextObject

this is sent, when a new Object is going to be visited.
Subclasses may redefine this to perform specific actions

 visitObject: anObject with: aParameter

visit an object. Subclasses must at least implement this method

** This method raises an error - it must be redefined in concrete classes **

 visitBehavior: aSymbol with: aParameter

visit a class

 visitBitArray: aByteArray with: aParameter

visit an absolute time value

 visitBlock: aBlock with: aParameter

 visitBoolean: aBoolean with: aParameter

visit a Boolean

 visitByteArray: aByteArray with: aParameter

visit a ByteArray value

 visitCharacter: aCharacter with: aParameter

visit a Character

 visitCollection: aCollection with: aParameter

visit a Collection

 visitDate: aDate with: aParameter

visit a date value

 visitDictionary: aDictionary with: aParameter

visit a Dictionary

 visitFloat: aFloat with: aParameter

visit a Float

 visitFraction: aFraction with: aParameter

visit a Fraction

 visitInteger: anInteger with: aParameter

visit an Integer

 visitInterval: anInterval with: aParameter

intervals are a special flavor of sequenceable collection (saving memory)
We treat it as SequenceableCollection by default.
Encoders that do a dense representation, redefine this to #visitObject

 visitNilWith: aParameter

visit a nil

 visitNumber: aNumber with: aParameter

visit an Integer

 visitSequenceableCollection: aCollection with: aParameter

visit a SequenceableCollection

 visitSet: aCollection with: aParameter

visit a Set

 visitStream: aStream with: aParameter

visit a Stream

 visitString: aString with: aParameter

visit a String

 visitSymbol: aSymbol with: aParameter

visit a Symbol

 visitTimestamp: aTimestamp with: aParameter

visit an timestamp value