Expand description
Fine-grained and reversible struct transactions.
This crate offers a Track macro that structs can derive to generate the
plumbing needed to precisely track changes to fields. Calling
edit() returns a draft that stores edits separately from
the underyling struct, such that no values are written.
When apply() is called on the draft, edits are applied to the
base struct. Each replaced value is returned to the caller as a Change in
a ChangeSet. This changeset can then be re-applied to a struct of the same
type, which replaces fields with values from the ChangeSet. This operation
produces a new ChangeSet, allowing for the implementation of an undo-redo
paradigm.
Example
use cset::Track;
#[derive(Track)]
struct Foo {
x: usize,
#[track(flatten)]
bar: Bar,
}
#[derive(Track)]
struct Bar {
y: usize,
}
let mut foo = Foo::new(10, Bar::new(42));
// Enter the non-destructive editing mode
let mut foo_draft = foo.edit();
foo_draft.set_x(42);
foo_draft.edit_bar().set_y(1024);
// Drop the draft to rollback, or apply the changes with `.apply()`
let undo_changeset = foo_draft.apply();
assert_eq!(foo, Foo::new(42, Bar::new(1024)));
let redo_changeset = foo.apply(undo_changeset);
assert_eq!(foo, Foo::new(10, Bar::new(42)));
foo.apply(redo_changeset);
assert_eq!(foo, Foo::new(42, Bar::new(1024)));