Property Operations

Properties can be changed, deleted or checked with property operations.

Check property value

A Check compares the complete property value at its position in the change request, including changes preceding it. A failed check rolls back that record’s changes. Empty lists, sets, and maps differ from absent properties; list order matters, while sets and maps compare their complete contents.

Check if firstName is John

Check(
    Person.ref { firstName } with "John",
    Person.ref { lastName } with "Smith"
)

Change property value

Use Change to update a property value.

Change(
    Person.ref { firstName } with "Jane",
    Person.ref { lastName } with "Doe"
)

A whole list, set, or map can also be replaced with Change(ref with replacement). An empty replacement keeps the property present and must satisfy its size constraints. Use the member operations below for incremental edits.

Changing an embedded value replaces that complete value, including when the replacement is empty. Use a child reference to change selected fields. Ordered operations and reference-value pairs observe earlier changes in the same request; Values.change preserves its original values and caller-owned replacement collections and inserted values. The separate Values.copy API retains its embedded merge behavior.

In Values.change, a wildcard child operation applies the complete child path independently to every matching map value or list item. A typed child reference addresses the active case only: deleting an inactive child has no effect, while setting it rejects the change. Replace the multi-type parent to select a new case.

Deletion

Set a property to null to delete it.

Change(
    Person.ref { firstName } with null
)

Changes on Map, List and Set properties

Map, List and Set properties have specialised change operations documented on their respective pages.

Copying and replacing values

Values.copyWithValue(index, value) replaces one complete root value, including an embedded record. Fields omitted from a replacement stay absent. Passing Unit removes that root. Values.copy { ... } retains its existing embedded patch behavior.

Value ownership

Each emptyValues() result owns its mutable item collection. The copyWithOwnedValues() extensions copy built-in Values, collection and typed value operands when a value or change must outlive its caller’s buffers.