class UndoManager

Responsibilities

Manage undo stack
Manage redo stack
clear redo stack when new undo command is added

Collaborators

Command

Attributes

redo_stack[R]

undo_stack[R]

Public Class Methods

new(undo_stack = []) click to toggle source

Initializes a new UndoManager. @param undo_stack [Array, optional]

# File lib/undo_manager.rb, line 13
def initialize(undo_stack = [])
  @undo_stack = undo_stack
  @redo_stack = []
  @total_ops_counter = 0
end

Public Instance Methods

can_redo?() click to toggle source

Returns true if there is at least one command to be redone.

# File lib/undo_manager.rb, line 20
def can_redo?
  @redo_stack.any?
end

can_undo?() click to toggle source

Returns true if there is at least one command to be undone.

# File lib/undo_manager.rb, line 25
def can_undo?
  @undo_stack.any?
end

record_new_command(command) click to toggle source

Pushes a new command onto the undo_stack. @param command [#do, undo] a command object that responds to do and undo @return [Integer] number of total commands

# File lib/undo_manager.rb, line 32
def record_new_command(command)
  @redo_stack = [] # clear redo stack
  @undo_stack.push(command)
end

redo_command() click to toggle source

Redoes command at top of redo_stack. @return [Command, nil] the redone command or nil if nothing was redone

# File lib/undo_manager.rb, line 39
def redo_command
  o = @redo_stack.pop
  if o
    o.do # redo the command
    @undo_stack.push(o)
  end
  o
end

undo_command() click to toggle source

Undoes command at top of undo_stack. @return [Command, nil] the undone command or nil if nothing was undone

# File lib/undo_manager.rb, line 50
def undo_command
  o = @undo_stack.pop
  if o
    o.undo # undo the command
    @redo_stack.push(o)
  end
  o
end