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Items

property Items[Index: Integer]: TIdMessagePart read write; default;

Example​

procedure ReadFirstPart(const Parts: TIdMessageParts;
  var Value: Variant);
begin
  if Parts.Count > 0 then
    Value := Parts.Items[0].ContentType
  else
    Value := '';
end;

Usage​

Items gets a borrowed message part by zero-based index or Assign-copies a source into the existing destination object without replacing ownership.

Additional Technical Info​

Items is the zero-based default indexed property for the collection. A read returns the existing TIdMessagePart descendant at Index; Parts[Index] and Parts.Items[Index] are equivalent in scripts.

The returned object is borrowed and owned by the collection. Do not free it. Removing/clearing the item or destroying the owning message invalidates the reference. An index below zero or greater than or equal to Count raises the inherited collection bounds exception.

A write has unusually important semantics: inherited TCollection.SetItem calls Assign on the existing destination item. It does not replace the object, move the source, change collection ownership or preserve every possible descendant-specific resource. Runtime types control the result:

  • TIdMessagePart.Assign copies header/metadata state, including header lists, character set, filename and name.
  • TIdText.Assign additionally copies its body.
  • attachment backing storage is not copied by the base implementation; assigning attachment metadata therefore must not be treated as cloning the attached bytes or file.
  • nil or incompatible sources can raise, and a multi-field assignment is not transactional.

Assignment can change fields used during encoding and counting without refreshing AttachmentCount or TextPartCount. Call CountParts afterward when cached counts matter.

Reads are normally constant-time. Assignment cost depends on copied headers/body and can be linear in their content. Neither access nor assignment is thread-safe. The source-reviewed example bounds-checks before borrowing the first item and was not runtime-tested.

External references

Created 2026-07-15