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EndUpdate

procedure EndUpdate;

Example​

procedure BatchChanges(const Items: TCollection);
begin
  Items.BeginUpdate;
  try
    // Perform one or more collection changes.
  finally
    Items.EndUpdate;
  end;
end;

Usage​

EndUpdate ends one TCollection update-batch level and triggers the deferred collection update when balance reaches zero.

Parameters and result

It has no parameters or return value. It must be called once, and only once, for each completed BeginUpdate.

Behaviour

  • Nested batches do not release updates until the outermost matching call reaches zero.
  • The deferred update callback runs synchronously before EndUpdate returns.
  • The counter is decremented before the callback, so a callback exception leaves the counter at zero.
  • Always place it in the finally block paired with BeginUpdate.

Errors and edge cases

There is no unmatched-call exception. Calling EndUpdate at balance zero makes the counter negative; later Changed calls then remain suppressed because the counter is not zero. Callback exceptions propagate.

Additional Technical Info​

EndUpdate is a script-visible method declared on hidden ancestor TCollection. Visible descendant classes inherit it even though Classes/Common is intentionally omitted from the Velox and Docusaurus Code Library menus.

EndUpdate closes one nesting level opened by BeginUpdate. When the internal counter becomes exactly zero, Delphi calls the collection's normal virtual Update(nil) path through Changed.

Implementation trace

Studio 37.0 performs an unchecked Dec(FUpdateCount) and then calls Changed. Changed calls Update(nil) only when the counter equals zero; it does not test for a negative counter.

Side effects and ownership

Mutates the update counter and can synchronously invoke descendant Update behaviour. The method itself does not commit or roll back mutations.

Performance and concurrency

Counter work is O(1), followed by descendant update cost when balance reaches zero. It is not a lock and supplies no cross-thread safety.

Remarks

This entry describes the installed Delphi Studio 37.0 terminal reached by the Velox-modified PascalScript registration. Free Pascal is linked for compatible Object Pascal context; where implementations differ, the traced Delphi behaviour above is authoritative. The example is source-reviewed and non-destructive except where the named operation is inherently destructive.

Related entries

  • BeginUpdate opens the required matching level.
  • Clear uses an internally balanced batch around item destruction.

External references

Created 2026-07-15