Migration constructor
Migration(
- Operation forward, {
- dynamic reverse,
Construct a migration from its constituent forward Operation and
optionally reverse
.
For use in scenarios where the database may be downgraded, reverse
is
the operation that "undoes" the forward operation. It not always
necessary or possible for the forward and reverse operations to be
true inverses. Instead, the reverse should restore the database back to
a suitable state such that A) prior versions of code that do not expect
this operation may operate and B) the upgrade can be reapplied as
expected.
The default reverse
operation is noop.
Implementation
Migration(this.forward, {reverse})
: this.reverse = reverse ?? Operation<void>(noop);