Sequel Orderable Plugin
Allows for model instances to be part of an ordered list, based on a ‘position’ field in the database.
Basic Usage
Load the plugin into the model:
is :orderable
Given:
class Item < Sequel::Model(:items)
set_schema do
primary_key :id
varchar :name
int :position
end
is :orderable, :field => :position
end
item = Item
The plugin provides access to the previous and next item in the list
item.next
item.prev
And methods to change the position of an item (and update affected items accordingly)
item.move_to(new_position)
item.move_to_top
item.move_to_bottom
item.move_up
item.move_down
Scoping
You can scope the position field by another field.
For example, to allow each user to have their own a distinct orderable list:
class UserItem < Sequel::Model(:items)
set_schema do
primary_key :id
varchar :name
int :user_id
int :pos
end
is :orderable, :field => :pos, :scope => :user_id
end
All the defined methods will operate within the ‘user_id’ field’s scope.
Examples
# Input: irb require “sequel”
DB = Sequel.sqlite class Item < Sequel::Model(:items)
set_schema do
primary_key :id
varchar :name
int :position
end
is :orderable, :field => :position
end
Item.create_table! Item.create :name => “alice”, :position => 2 Item.create :name => “bob”, :position => 1 Item.create :name => “charlie”, :position => 4 Item.create :name => “darwin”, :position => 3
Item.print
Item[:name => “alice”].move_down Item.print Item[:name => “darwin”].move_to_top Item.print Item[:name => “alice”].next Item.print Item[:name => “bob”].prev Item.print Item[:name => “darwin”].move_to(3) Item.print Item[:name => “bob”].move_to_bottom Item.print
# Output >> Item.print --
——---------
|id|name |position| --
——---------
| 2|bob | 1| | 1|alice | 2| | 4|darwin | 3| | 3|charlie| 4| --
——---------
> nil
>> Item[:name => “alice”].move_down
> :position=>3
>> Item.print --
——---------
|id|name |position| --
——---------
| 2|bob | 1| | 4|darwin | 2| | 1|alice | 3| | 3|charlie| 4| --
——---------
> nil
>> Item[:name => “darwin”].move_to_top
> :position=>1
>> Item.print --
——---------
|id|name |position| --
——---------
| 4|darwin | 1| | 2|bob | 2| | 1|alice | 3| | 3|charlie| 4| --
——---------
> nil
>> Item[:name => “alice”].next
> #<Item:0x119dbc8 @values=:name=>“charlie”, :id=>3, newfalse
>> Item.print --
——---------
|id|name |position| --
——---------
| 4|darwin | 1| | 2|bob | 2| | 1|alice | 3| | 3|charlie| 4| --
——---------
> nil
>> Item[:name => “bob”].prev
> #<Item:0x1184bb4 @values=:name=>“darwin”, :id=>4, newfalse
>> Item.print --
——---------
|id|name |position| --
——---------
| 4|darwin | 1| | 2|bob | 2| | 1|alice | 3| | 3|charlie| 4| --
——---------
> nil
>> Item[:name => “darwin”].move_to(3)
> :position=>3
>> Item.print --
——---------
|id|name |position| --
——---------
| 2|bob | 1| | 1|alice | 2| | 4|darwin | 3| | 3|charlie| 4| --
——---------
> nil
>> Item[:name => “bob”].move_to_bottom
> :position=>4
>> Item.print --
——---------
|id|name |position| --
——---------
| 1|alice | 1| | 4|darwin | 2| | 3|charlie| 3| | 2|bob | 4| --
——---------