Class TX3DSimpleMultField

DescriptionHierarchyFieldsMethodsProperties

Unit

Declaration

type TX3DSimpleMultField = class(TX3DMultField)

Description

Field holding multiple values. Remember that such field may always have any number of items, including zero.

Note that we keep MF fields contents in TFPSList or TCastleStringList instances (RawItems in this class, also accessible as Items (with more concrete class) in descendants). This means that they are in compact form, easy for reading, or even for feeding the list into OpenGL. That's the main reason why I did not simply implement TX3DSimpleMultField as a descendant of TX3DSingleFieldsList: A long list of vertexes, MFVec3f, would be kept as a list of pointers to a lot of TSFVec3f instances. This would be quite memory-consuming, and very uncomfortable for access. On the contrary, current implementation keeps all these vertexes inside one TVector3SingleList instance, that internally keeps all items in one continuos piece of memory.

Descendants implementors notes: to make new descendant:

  • In CreateUndefined you have to initialize FItemClass and create RawItems. In destructor of this class, RawItems are freed, so don't worry about this.

  • Override RawItemsAdd.

  • If your ItemClass doesn't work 100% correctly when it's initialized by CreateUndefined, you may have to override CreateItemBeforeParse. Fortunately, VRML specification was careful to choose as multi-valued field types' only fields that can behave nicely when initialized by CreateUndefined (and in fact VRML 2.0 removed the "bad fields" entirely).

  • Not strictly required, but usually it's comfortable to have a constructor that allows you to init default field value from some "array of TXxx".

Hierarchy

Overview

Fields

Public RawItems: TObject;

Methods

Public procedure ParseValue(Lexer: TX3DLexer; Reader: TX3DReader); override;
Public destructor Destroy; override;
Public function Equals(SecondValue: TX3DField; const EqualityEpsilon: Double): boolean; override;
Public procedure ParseXMLAttributeLexer(Lexer: TX3DLexer; Reader: TX3DReader); override;

Properties

Public property ItemClass: TX3DSingleFieldClass read fItemClass;

Description

Fields

Public RawItems: TObject;

Items of this field. Either TFPSList or TCastleStringList.

Descendants implementors notes: You have to initialize this field in descendants' constructor, it will be always freed in our destructor.

Methods

Public procedure ParseValue(Lexer: TX3DLexer; Reader: TX3DReader); override;

Parse MF field. This class handles parsing fully, usually no need to override this more in descendants. It uses ItemClass.Parse method.

Public destructor Destroy; override;
 
Public function Equals(SecondValue: TX3DField; const EqualityEpsilon: Double): boolean; override;

Checks equality between this and SecondValue field. In addition to inherited(Equals), this also checks that Count and ItemClass are equal. All descendants must check for equality every item on SecondValue.Items[I] and Items[I].

Public procedure ParseXMLAttributeLexer(Lexer: TX3DLexer; Reader: TX3DReader); override;
 

Properties

Public property ItemClass: TX3DSingleFieldClass read fItemClass;

A corresponding SF field class. All items that will be passed to RawItemsAdd will be of this class.


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