Module: ActsAsList::InstanceMethods

Defined in:
lib/acts_as_list.rb

Overview

All the methods available to a record that has had acts_as_list specified. Each method works by assuming the object to be the item in the list, so chapter.move_lower would move that chapter lower in the list of all chapters. Likewise, chapter.first? would return true if that chapter is the first in the list of all chapters.

Instance Method Summary collapse

Instance Method Details

#decrement_position ⇒ Object

Decrease the position of this item without adjusting the rest of the list.



135
136
137
138
 
# File 'lib/acts_as_list.rb', line 135

def decrement_position
  return unless in_list?
  update_attribute position_column, self.send(position_column).to_i - 1
end

#first? ⇒ Boolean

Return true if this object is the first in the list.

Returns:

  • (Boolean) 


141
142
143
144
 
# File 'lib/acts_as_list.rb', line 141

def first?
  return false unless in_list?
  self.send(position_column) == 1
end

#higher_item ⇒ Object

Return the next higher item in the list.



153
154
155
156
157
158
 
# File 'lib/acts_as_list.rb', line 153

def higher_item
  return nil unless in_list?
  acts_as_list_class.find(:first, :conditions =>
    "#{scope_condition} AND #{position_column} < #{send(position_column).to_s}", :order => "#{position_column} DESC"
  )
end

#in_list? ⇒ Boolean

Test if this record is in a list

Returns:

  • (Boolean) 


169
170
171
 
# File 'lib/acts_as_list.rb', line 169

def in_list?
  !send(position_column).nil?
end

#increment_position ⇒ Object

Increase the position of this item without adjusting the rest of the list.



129
130
131
132
 
# File 'lib/acts_as_list.rb', line 129

def increment_position
  return unless in_list?
  update_attribute position_column, self.send(position_column).to_i + 1
end

#insert_at(position = 1) ⇒ Object

Insert the item at the given position (defaults to the top position of 1).



76
77
78
 
# File 'lib/acts_as_list.rb', line 76

def insert_at(position = 1)
  insert_at_position(position)
end

#last? ⇒ Boolean

Return true if this object is the last in the list.

Returns:

  • (Boolean) 


147
148
149
150
 
# File 'lib/acts_as_list.rb', line 147

def last?
  return false unless in_list?
  self.send(position_column) == bottom_position_in_list
end

#lower_item ⇒ Object

Return the next lower item in the list.



161
162
163
164
165
166
 
# File 'lib/acts_as_list.rb', line 161

def lower_item
  return nil unless in_list?
  acts_as_list_class.find(:first, :conditions =>
    "#{scope_condition} AND #{position_column} > #{send(position_column).to_s}", :order => "#{position_column} ASC"
  )
end

#move_higher ⇒ Object

Swap positions with the next higher item, if one exists.



91
92
93
94
95
96
97
98
 
# File 'lib/acts_as_list.rb', line 91

def move_higher
  higher = higher_item
  return unless higher
  acts_as_list_class.transaction do
    self.update_attribute(position_column, higher.send(position_column))
    higher.increment_position
  end
end

#move_lower ⇒ Object

Swap positions with the next lower item, if one exists.



81
82
83
84
85
86
87
88
 
# File 'lib/acts_as_list.rb', line 81

def move_lower
  lower = lower_item
  return unless lower
  acts_as_list_class.transaction do
    self.update_attribute(position_column, lower.send(position_column))
    lower.decrement_position
  end
end

#move_to_bottom ⇒ Object

Move to the bottom of the list. If the item is already in the list, the items below it have their position adjusted accordingly.



102
103
104
105
106
107
108
 
# File 'lib/acts_as_list.rb', line 102

def move_to_bottom
  return unless in_list?
  acts_as_list_class.transaction do
    decrement_positions_on_lower_items
    assume_bottom_position
  end
end

#move_to_top ⇒ Object

Move to the top of the list. If the item is already in the list, the items above it have their position adjusted accordingly.



112
113
114
115
116
117
118
 
# File 'lib/acts_as_list.rb', line 112

def move_to_top
  return unless in_list?
  acts_as_list_class.transaction do
    increment_positions_on_higher_items
    assume_top_position
  end
end

#remove_from_list ⇒ Object

Removes the item from the list.



121
122
123
124
125
126
 
# File 'lib/acts_as_list.rb', line 121

def remove_from_list
  if in_list?
    decrement_positions_on_lower_items
    update_attribute position_column, nil
  end
end