_declare

The _declare virtual method creates a metadata variable in the underlying data store.

It implements declare. A ParamSpec is used to describe the variable. If the metadata shadows an object property, shadow should be true, otherwise false. It is acceptable for a subclass to provide additional variables which are implicitly declared, that is, they need not be declared using declare, however the pspec method must still retrieve a ParamSpec describing such variables. This method MUST be provided by the subclass.