Creating a linked list of unknown types

[seany]

Hi

I want to build a markdown/groff/troff renderer with a little bit of custom functionality.

I do not like HTML/Javascript, So I am trying to use the FPC graphics stack.

I have this in a file called TRenderObjects.pas.

Code: Pascal  [Select][+][-]

1. unit TRenderObjects;
2.  
3. {$mode ObjFPC}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils;
9.  
10. type
11.     Section         = class
12.       text            : Array of String;
13.       imgSrc          : Array of String;
14.       oper            : Array of String;
15.       textFont        : String;
16.       textColor       : Array of Integer;
17.       textFontVariant : (Bold, Italic, Underline, Strikethrough);
18.       isRendered      : Boolean;
19.  
20.     end;
21.     ImageBlob       = class
22.  
23.       // border
24.  
25.       borderWidth     : Integer;
26.       boderColor      : Array of Integer;
27.  
28.  
29.     end;
30.  
31.  
32. implementation
33.  
34. end.
35.                
36.  

In a second file called TDocument.pas, i want to have

Code: Pascal  [Select][+][-]

1. unit TDocument;
2.  
3. {$mode ObjFPC}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, TRenderObjects;
9.  
10. type
11.   markedDocument = class
12.     // Sections : Array of TRenderObjects.Section;
13.     SectionNodePTR : ^NodeStruct;
14.     NodeStruct  : packed record    // writing = instead of : in this line and the previous fails with message : expected = found
15.       rendObj   : T;
16.       ID        : Integer;
17.       Parent    : SectionNodePTR;
18.       Children  : Array of SectionNodePTR;
19.       end;
20.  
21.     public :
22.       var
23.          DocumentTree :  NodeStruct;
24.          procedure AppendChild (ChildObj : T);
25.   end;
26.  
27.  
28. implementation
29.  
30. end.      

I want to define a template of a tree in the class, and then use the append procedure to add either TRenderObjects.Section or TRenderObjects.ImageBlob. That is why I used T as a template Type. But this fails with:

Projekt kompilieren, Ziel: notebook: Exit code 1, Fehler: 7
tdocument.pas(15,19) Error: Identifier not found "T"
tdocument.pas(15,20) Error: Error in type definition
tdocument.pas(17,19) Error: Identifier not found "SectionNodePTR"
tdocument.pas(17,33) Error: Error in type definition
tdocument.pas(18,28) Error: Identifier not found "SectionNodePTR"
tdocument.pas(18,42) Error: Error in type definition
tdocument.pas(21,12) Fatal: Syntax error, "identifier" expected but ":" found


Please let me know how I can create a tree with unspecified types inside a class, initialize it, and then use an overloaded append or delete procedure to modify the tree. Thank you.

[VisualLab]

Suppose this is a generic tree. So each tree node will contain a list of child nodes. The number of child nodes in this list can be any number. I would use the existing generic classes from the FCL library to create the tree class. The tree class schema could be:

Code: Pascal  [Select][+][-]

1. {$mode Delphi}
2.  
3. interface
4.  
5. uses
6.   Classes, Generics.Collections;
7.  
8. TTreeNode<T> = class;
9.  
10. TSubNodeList = class(TObjectList<TTreeNode>);
11.  
12. TTreeNode<T> = class(TObject)
13. private
14.   FData: T;
15.   FSubNodes: TSubNodeList;
16.   procedure SetData(Value: T);
17. public
18.   constructor Create;
19.   destructor Destroy; override;
20.   property Data: T read FData write SetData;
21.   property SubNodes: TSubNodeList read FSubNodes;
22. end;
23.  
24. TDocumentTree<T> = class(TObject)
25. private
26.   FRoot: TTreeNode<T>;
27. public
28.   constructor Create;
29.   destructor Destroy; override;
30.   property Root: TTreeNode<T> read FRoot;
31. end;
32.  
33. implementation
34.  
35. constructor TTreeNode<T>Create;
36. begin
37.   FSubNodes := TSubNodeList.Create(True);
38. end;
39.  
40. destructor TTreeNode<T>Destroy;
41. begin
42.   FSubNodes.Free;
43. end;
44.  
45. constructor TDocumentTree<T>Create;
46. begin
47.   FRoot := TTreeNode.Create;
48. end;
49.  
50. destructor TDocumentTree<T>Destroy;
51. begin
52.   FRoot.Free;
53. end;

This is a very general outline.

[seany]

Thank you. I will use this and bump up this thread in future if i need some help.