TvxFileDef

type TvxFileDef = class(TvxDataDef);

Example

procedure ScriptEvent(var Value: Variant);
begin
  { In a script compiled with a file-backed Source. }
  if Source <> nil then
    Value := Source.FileType
  else
    Value := -1;
end;

Usage

TvxFileDef represents a Velox-provided flat, XML, EDI, Excel or JSON data definition used as a flow Source or Dest.

Errors, security and performance

Schema/template paths are trusted configuration. Relative traversal, inaccessible mapped drives, unexpected schemas/templates and secrets in paths/password-protected workbooks can produce I/O, parsing or disclosure risk. Process methods are cheap except for possible base-directory creation; actual XML/Excel work is blocking and can be significantly more expensive.

Additional Technical Info

TvxFileDef is Velox's data-definition module for flat text, XML, EDI, Excel and JSON files. The scripter registers Source and/or Dest as this class when the configured flow endpoint is file-backed.

Declaration and acquisition

Velox creates, loads, transfers and owns these modules. The scripting import registers no constructor; do not instantiate, free or retain a Source/Dest reference beyond its execution context.

Members declared by its DataDef/module ancestors remain documented at those declaring paths. This page covers only the generated TvxFileDef surface.

Format and engine lifecycle

FileType is the format discriminator:

File type	Engine selected for later load/save
fftFlatFile	Flat/fixed/delimited text engine
fftXMLFile	XML engine with optional XSD loading/validation
fftEDIFile	EDI engine
fftExcelFile	Excel workbook engine
fftJSONFile	JSON engine

The file engine is created for a load/save operation from the current type and then freed. A failed/unsupported type can leave no engine; configuration should be fixed rather than changed opportunistically during active processing.

Construction also creates XML/MSXML schema objects, assignment lists and XML processing state. Reset returns FileNo to 1 and clears per-run design/navigation state. Transfer copies configuration into the execution instance and normalises the legacy fftExcel value to fftExcelFile.

Schema and template processing

• ProcessXSDSchema resolves the configured XSD's default-directory token to Velox's application Schema path.
• ProcessExcelTemplate resolves the Excel template token to the application Excel path.

These methods do not perform general action/data tag expansion. If the default token is present, resolving the application path can create its base directory. XSD/Excel consumers perform file checks and parsing/opening later.

Mutable state and side effects

• FileNo increments on every read and is independent of FileCon's filename counter.
• Writing FileType changes future format/engine selection but does not rebuild an already active DataModule, schema cache or file engine.
• File loads/saves, XSD parsing and Excel template opening use the active Log, FileCon and service/process filesystem identity.
• Source/Dest objects and their datasets are mutable execution state, not thread-safe shared configuration.

Related entries

• Source and Dest — context-owned module references.
• TvxFileType — registered format enumeration.
• TvxFileCon — file paths, naming and current I/O state.

Created 2026-07-15