ExceptionType

function ExceptionType: TIFException;

Example

procedure ScriptEvent(var Value: Variant);
begin
  try
    RaiseException(erCustomError, 'Fictional validation failure');
  except
    if ExceptionType = erCustomError then
      Value := ExceptionParam
    else
      RaiseLastException;
  end;
end;

Usage

ExceptionType returns the TIFException value for the current Velox scripting runtime exception.

Returns

One of the current TIFException enumeration values:

Ordinal	Value	Runtime category
0	ErNoError	No saved VM error
1	erCannotImport	Required imported function could not be resolved
2	erInvalidType	Invalid value type
3	ErInternalError	Velox script-engine failure
4	erInvalidHeader	Invalid compiled-script header
5	erInvalidOpcode	Unknown bytecode operation
6	erInvalidOpcodeParameter	Invalid bytecode operation argument
7	erNoMainProc	No main procedure is available
8	erOutOfGlobalVarsRange	Global-variable index is out of range
9	erOutOfProcRange	Procedure index is out of range
10	ErOutOfRange	General VM range failure
11	erOutOfStackRange	Stack index is out of range
12	ErTypeMismatch	Runtime value/type mismatch
13	erUnexpectedEof	Compiled data ended unexpectedly
14	erVersionError	Compiled-script/runtime version mismatch
15	ErDivideByZero	Division by zero
16	ErMathError	Other mapped arithmetic failure
17	erCouldNotCallProc	Procedure invocation failed
18	erOutofRecordRange	Record-field index is out of range
19	erOutOfMemory	Mapped out-of-memory failure
20	erException	General Velox/host exception mapped by the VM
21	erNullPointerException	Nil pointer/object access
22	erNullVariantError	Invalid Null Variant operation
23	erInterfaceNotSupported	Requested interface is unavailable
24	erCustomError	Explicit or mapped custom runtime error

Use ExceptionToString for the exact display text. Some categories describe Velox script-engine failures that a script cannot deliberately reproduce.

Errors

There is no separate missing-state exception. An available but empty frame returns ErNoError; VM stack failures can still propagate.

Additional Technical Info

ExceptionType returns the PascalScript virtual machine's saved TIFException category. It identifies a runtime error code, not a Delphi exception class and not a script-visible exception object.

The example handles only the deliberately expected custom category and re-raises anything else. It is source-reviewed and was not executed by the documentation workflow.

Implementation

The compiler defines TIFException in the same order as the runtime's TPSError enumeration and registers ExceptionType as built-in dispatch 32. The runtime calls TPSExec.LastEx:

1. If an exception-handler frame exists, it returns the top frame's ExceptionData.
2. Otherwise it returns the executor-level ExEx field.
3. Dispatch stores the enumeration ordinal as a 32-bit integer in the function result.

When an error enters an except block, the VM copies the category to the handler frame and resets the executor-level ExEx to ErNoError. This is why the saved type remains readable from the active handler.

Behaviour

• A newly created handler frame is zero-initialised, so calling ExceptionType in its protected try sequence before a failure returns ErNoError.
• Inside an active handler, it returns the category saved for that handler until the frame is removed or reused for propagation.
• Nested try regions expose the top frame only.
• Reading the type does not mark the exception handled, clear it or alter normal control flow.

Edge cases and quirks

• TIFException is PascalScript's VM error taxonomy. Delphi classes such as EDivByZero may be translated into one of these values, and several different native failures can therefore share a category.
• Host or imported-code exceptions can be caught, translated or logged at an event boundary rather than becoming a script-catchable value. The function does not guarantee that every process-level exception is visible in a script handler.
• ErNoError means that the inspected frame/state has no saved VM error. It does not prove that prior Flow work succeeded or that earlier side effects were rolled back.
• Enumeration ordinals are implementation data. Store the meaningful category/name when durable diagnostics are required rather than persisting the number.

Side effects

None. The function reads the current executor or top handler frame.

Performance and concurrency

The lookup is constant-time and allocates no user-visible object. Exception state belongs to the current script executor and does not provide a lock or thread-safety boundary.

Remarks

Branch only on categories your script can handle meaningfully. For unexpected categories, preserve the original failure with RaiseLastException instead of replacing it with a generic message.

Related entries

• ExceptionParam returns the text associated with the current category.
• ExceptionToString maps the category and parameter to runtime display text.
• RaiseException accepts a TIFException value to create VM error state.
• try..except explains availability and propagation of the handler state.

Created 2026-07-15