cset

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 Trackable::edit() returns a Draft that stores edits separately from the underyling struct, such that no values are written.

When .commit() 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, Trackable, Draft};

#[derive(Track)]
struct Foo {
    bar: i32,
}

// Create a new `Foo` as normal
let mut foo = Foo { bar: 0 };

// Make a tracked change
let undo_cset = foo.edit().set_bar(42).commit();
assert_eq!(foo.bar, 42);

// Undo the change by applying the returned changeset
let redo_cset = foo.apply_changeset(undo_cset);
assert_eq!(foo.bar, 0);

// Redo the change by applying the changeset produced by undoing
foo.apply_changeset(redo_cset);
assert_eq!(foo.bar, 42);

Project status

This project is early in development and API changes should be expected.