Snapshot

A lightweight single-depth object state capture. The take_snapshot method reads the object‘s state, which is generally it‘s collection of instance variables, and returns them in a hash. The state can be restored with apply_snapshot.

Usage

  Customer = Struct.new("Customer", :name, :address, :zip)
  joe = Customer.new( "Joe Pitare", "1115 Lila Ln.", 47634 )

  # simple transactions
  joe_snap = joe.take_snapshot
  begin
    do_something_with( joe )
  rescue
    joe.apply_snapshot( joe_snap )
  end

  joe_snap[:name]     => "Joe Pitare"
  joe_snap[:address]  => "1115 Lila Ln."
  joe_snap[:zip]      => 47634

Details

Class Snapshot simply represents a collection of objects from which snapshots were taken via their methods take_snapshot. It provides methods to add an object to a snapshot (Snapshot#add) as well as to restore all objects of the snapshot to their state stored in the snapshot (method Snapshot#restore).

In Wee, this class is used to backtracking the state of components (or decorations/presenters). Components that want an undo-facility to be implemented (triggered for example by a browsers back-button), have to overwrite the Wee::Component#backtrack_state method.

Todo

Perhaps extend to offer multiple depths.
Should key consitancy be enforced? Currently Struct‘s will have symbol keys while other classes will have string keys in the form of "@name".
Add other core classes.
Convert to Kernel#to_data ?
I‘ve been thinking about renaming this to State.

Authors

Michael Neumann

Copying

Ruby License

This module is free software. You may use, modify, and/or redistribute this software under the same terms as Ruby.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.