A precondition on a document, used for conditional operations.
- exists ↔ bool
When set to
true, the target document must exist. When set to
false, the target document must not exist.read / write
- hashCode → int
The hash code for this object. [...]
- runtimeType → Type
A representation of the runtime type of the object.
- updateTime ↔ String
When set, the target document must exist and have been last updated at
read / write