NullableString

Overview

Abstract data type

A sequence of characters, or a null value. NullableString is abstract and has two concrete subtypes:

• a String is an actual value for a sequence of characters;

• a NullString is a null value that explicitly indicates the absence of a sequence of characters.

Subtypes

• NullString

• String

Implementation in Proteus Schema

The Proteus Schema implementation of NullableString depends on the Proteus Schema implementations of the data attributes with type NullableString.

• NullableString is the type of the Value attribute of CustomStringAttribute. CustomStringAttribute is implemented as a DEXPI custom generic attribute.

• All other data attributes with type NullableString are implemented as DEXPI generic attributes. For example, see the LocalNoteIdentifier attribute of Note.

Note that there are further data attributes with type String instead of NullableString. See the Proteus Schema implementation of String for a list of these special cases.