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Dest

Dest: TvxFileDef

Example​

procedure ScriptEvent(var Value: variant);
begin
  if Dest <> nil then
    Value := Dest.ModuleName
  else
    Value := Null;
end;

Usage​

Provides the current destination file or database definition for the script context.

Ownership, side effects and errors

Velox owns the data definition. Never free it, retain it beyond execution or replace the public reference. Reading ModuleName is simple state access, but other members can open datasets/files, alter state or raise configuration/I/O exceptions. Those contracts belong to the definition/member being used.

Additional Technical Info​

Dest exposes the live destination data-definition object supplied to the current scripter. The concrete compile-time/runtime class can be TvxFileDef or TvxDBDef, depending on the configured context.

Indexed and effective declarations

The generated Code Library index records the default declaration:

During actual compilation, Velox instead registers:

Dest: TvxDBDef   // when FDest is a database definition
Dest: TvxFileDef // when it is a file definition or no instance is set

This source-dependent declaration is material: members specific to one subclass are available only when the script compiles for that subclass. Common module/data-definition members such as ModuleName are the portable choice.

Implementation

RegisterVariables examines the current FDest object and registers the corresponding class. SetVariableInstances binds the public name only when that object is assigned. The declaration is still present with the default file-definition type when no instance exists, allowing reusable script source to compile.

Before compilation, if no destination has been supplied, SetScript assigns FDest := FSource. The destination then points to exactly the source object.

Behaviour and availability

  • The reference can be nil/unbound in contexts without a destination definition; check it before member access.
  • The object represents live host configuration/execution state, not a detached copy.
  • Dest may alias Source exactly. When it does, property changes and method effects through either name affect the same object.
  • File and database definitions expose different specialized members. Do not assume the indexed TvxFileDef type describes every execution.
  • The reference is scoped to the compiled/executing scripter and can differ between actions or recompilations.
  • Treat the reference as context, not authorization to access arbitrary files or databases.

Performance and concurrency

Retrieving the bound reference is constant-time. The underlying object is mutable and tied to its action/scripter; it is not a general cross-thread data transfer object.

Related entries

  • Source exposes the source definition and may be the same instance.
  • DBCon derives the first current database connection from Source.
  • FileCon is a separately injected file-connection accessor.
Created 2026-07-15