Class: Innodb::List::ListCursor

Inherits:
Object
  • Object
show all
Defined in:
lib/innodb/list.rb

Overview

A list iteration cursor used primarily by the Innodb::List #cursor method implicitly. Keeps its own state for iterating through lists efficiently.

Instance Method Summary collapse

Constructor Details

#initialize(list, node = nil) ⇒ ListCursor

Returns a new instance of ListCursor.



137
138
139
140
 
# File 'lib/innodb/list.rb', line 137

def initialize(list, node=nil)
  @list   = list
  @cursor = node
end

Instance Method Details

#next ⇒ Object

Return the next entry from the current position, and advance the cursor position to the returned entry. If the cursor is currently nil, return the first entry in the list and adjust the cursor position to that entry.



165
166
167
168
169
170
171
 
# File 'lib/innodb/list.rb', line 165

def next
  if @cursor
    @cursor = @list.next(@cursor)
  else
    @cursor = @list.first
  end
end

#prev ⇒ Object

Return the previous entry from the current position, and advance the cursor position to the returned entry. If the cursor is currently nil, return the last entry in the list and adjust the cursor position to that entry.



153
154
155
156
157
158
159
 
# File 'lib/innodb/list.rb', line 153

def prev
  if @cursor
    @cursor = @list.prev(@cursor)
  else
    @cursor = @list.last
  end
end

#reset ⇒ Object

Reset the list cursor to its default starting state, which will allow iteration forwards from the first entry (using #next) or backwards from the last entry (using #prev).



145
146
147
 
# File 'lib/innodb/list.rb', line 145

def reset
  @cursor = nil
end