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Erase

procedure Erase;

Example​

procedure ScriptEvent(var Value: variant);
var
  Payload: TJSONObject;
begin
  Payload := TJSONObject.CreateFromString('{"temporary":true}');
  try
    Payload.Erase;
    Payload.AddString('status', 'ready');
    Value := Payload.AsString;
  finally
    Payload.Free;
  end;
end;

Usage​

Erase frees every owned field while retaining the same always-non-null object instance and its name.

Additional Technical Info​

Erase clears the owning value list. Every child and descendant is freed, ValueCount becomes zero and all previously borrowed child references become invalid.

The TJSONObject instance remains allocated and can be repopulated. Its inherited Name is unchanged. Erase does not write the private base null bit, but objects always read IsNull=False and serialize their fields regardless of that storage. Virtual inherited Clear dispatches to the object override, which calls this same method; unlike scalar TJSONValue.Clear, it cannot make the object semantically null. Script NotNull is misbound and reads false, so use not Payload.IsNull when a positive predicate is required.

An erased object immediately serializes through the known empty-object defect as } rather than {}. Add at least one valid field before emitting it, or handle empty output at a standards-compliant boundary.

Erasing an already empty object is safe. The method is not thread-safe and must not race with readers or writers holding child references.

External references

Created 2026-07-20