Documentation:Allow Null: Difference between revisions

Allow Null

Latest revision as of 05:05, 13 March 2025

Allow null sets an attribute's nullability, i.e. if this attribute should be able to hold "no value". It affects both the in-memory value (it will show up with a question mark at the end of the type, like Boolean?).

In C# and OCL, it is a bit tricky to know to check for both null and '' (empty string) for strings. Hence, the ->isnullorempty operator on string is good to use.

Nullability is at its best for numbers - helping the user to distinguish if someone wrote 0 or no-one has written anything yet...

Read more about Initial values and Default Database values for a fuller explanation of the properties InitialValue, DefaultDBValue and Allow Null.

This page was edited 1 days ago on 03/13/2025. What links here

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 '''Allow null''' sets an attribute's nullability, i.e. if this attribute should be able to hold "no value". It affects both the in-memory value (it will show up with a question mark at the end of the type, like Boolean?).
-In c# and ocl its a bit tricky to know to check for both null and <nowiki>''</nowiki> (empty string) for strings - hence the ->isnullorempty operator on string is good to use.
+In C# and OCL, it is a bit tricky to know to check for both null and <nowiki>''</nowiki> (empty string) for strings. Hence, the ->isnullorempty operator on string is good to use.
-Nullability is at its best for numbers - helping user to distinguish if someone wrote 0 or no-one has written anything yet...
+Nullability is at its best for numbers - helping the user to distinguish if someone wrote 0 or no-one has written anything yet...
-Read more about [[Initial values and Default Database values|'''Initial values''' and '''Default Database values''']] for a fuller explanation of the properties [[InitialValue]], [[DefaultDBValue]] and [[Allow Null]]
+Read more about [[Documentation:Initial values and Default Database values|'''Initial values''' and '''Default Database values''']] for a fuller explanation of the properties [[Documentation:InitialValue|InitialValue]], [[Documentation:DefaultDBValue|DefaultDBValue]] and Allow Null.
 {{Edited|July|12|2025}}
+[[Category:Database]]