Crate undo

Provides undo-redo functionality with dynamic dispatch and automatic command merging.

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. Both linear and non-linear undo-redo functionality is provided through the Record and History data structures.

Contents

• Command provides the base functionality for all commands.
• Record provides linear undo-redo functionality.
• History provides non-linear undo-redo functionality that allows you to jump between different branches.
• Queue wraps a Record or History and extends them with queue functionality.
• Checkpoint wraps a Record or History and extends them with checkpoint functionality.
• Configurable display formatting is provided when the display feature is enabled.
• Time stamps and time travel is provided when the chrono feature is enabled.

Concepts

• Commands can be chained before they are applied using the Chain structure. This makes it easy to build complex operations from smaller ones by combining them into a single command that can be applied, undone, and redone in a single step.
• 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.
• The target can be marked as being saved to disk and the data-structures can track the saved state and tell the user when it changes.
• The amount of changes being tracked can be configured by the user so only the n most recent changes are stored.

Examples

Add this to Cargo.toml:

[dependencies]
undo = "0.39"

And this to main.rs:

use undo::{Command, Record};

struct Add(char);

impl Command<String> 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'))?;
    assert_eq!(record.as_target(), "abc");
    record.undo().unwrap()?;
    record.undo().unwrap()?;
    record.undo().unwrap()?;
    assert_eq!(record.as_target(), "");
    record.redo().unwrap()?;
    record.redo().unwrap()?;
    record.redo().unwrap()?;
    assert_eq!(record.as_target(), "abc");
    Ok(())
}

Structs

Chain	A chain of merged commands.
Checkpoint	A checkpoint wrapper.
Display	Configurable display formatting of structures.
History	A history of commands.
HistoryBuilder	Builder for a History.
Queue	A command queue wrapper.
Record	A record of commands.
RecordBuilder	Builder for a record.

Enums

Merge	Says if the command should merge with another command.
Signal	The signal sent when the record, the history, or the target changes.

Traits

Command

Base functionality for all commands.

Type Definitions

Result

A specialized Result type for undo-redo operations.