undo

Provides simple undo-redo functionality with dynamic dispatch.

It is an implementation of the command pattern, where all modifications are done by creating objects of commands that applies the modifications. All commands knows how to undo the changes it applies, and by using the provided data structures it is easy to apply, undo, and redo changes made to a target.

Features

• Command provides the base functionality for all commands.
• Record is a collection of commands and provides the undo-redo functionality.
• Queue wraps a record and extends it with queue functionality.
• Checkpoint wraps a record and extends it with checkpoint functionality.
• Commands can be merged after being applied to the data-structures by implementing the merge method on the command. This allows smaller changes made gradually to be merged into larger operations that can be undone and redone in a single step.
• Configurable display formatting using Display.
• The target can be marked as being saved to disk and the record can track the saved state and notify when it changes.
• The amount of changes being tracked can be configured by the user so only the N most recent changes are stored.

If you need more advanced features, check out the redo crate.

Examples

```rust use undo::{Command, Record};

[derive(Debug)]

struct Add(char);

impl Command for Add { fn apply(&mut self, s: &mut String) -> undo::Result { s.push(self.0); Ok(()) }

fn undo(&mut self, s: &mut String) -> undo::Result {
    self.0 = s.pop().ok_or("s is empty")?;
    Ok(())
}

}

fn main() -> undo::Result { let mut record = Record::default(); record.apply(Add('a'))?; record.apply(Add('b'))?; record.apply(Add('c'))?; asserteq!(record.target(), "abc"); record.undo()?; record.undo()?; record.undo()?; asserteq!(record.target(), ""); record.redo()?; record.redo()?; record.redo()?; assert_eq!(record.target(), "abc"); Ok(()) } ```

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.