Module: PriorityOrderScopes::ClassMethods

Defined in:
lib/priority_order_scopes.rb

Instance Method Summary collapse

Instance Method Details

#priority_order_scopes(col, dir = :asc) ⇒ Object

Include PriorityOrderScopes and call ‘priority_order_scopes’ with a column name (and optional direction) to create ‘priority_order`, `next` and `previous` scopes.

‘next and `previous` require a record to start from. They will use the current scope if passed as part of a chain (or if a default scope with an order clause is defined), or default to the priority order.

You can also call instance.next or instance.previous directly. This will always use the default scope or the priority order.



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# File 'lib/priority_order_scopes.rb', line 15

def priority_order_scopes(col, dir=:asc)
  @priority_order_column = col
  @priority_order_direction = dir
  
  class << self
    define_method :priority_order do
      reorder("#{table_name}.#{@priority_order_column} #{@priority_order_direction}")
    end
    
    define_method :next do |current|
      return unless current
      
      # use the current scope's order clause, if any, or the priority order
      order = scoped.order_clauses[0] || priority_order.order_clauses[0]
      # turn ["last_name DESC, first_name", "id"] into "last_name"
      order = order.split(", ")[0]
      operator = order =~ /desc/i ? '<' : '>'
      order_column = order.split(" ")[0].split(".").last
      
      where(
        "#{table_name}.#{order_column} #{operator} ?",
        current.send(order_column)
      ).
      limit(1)
    end
    
    define_method :previous do |current|
      return unless current
      
      # use the current scope's order clause, if any, or the priority order
      order = scoped.order_clauses[0] || priority_order.order_clauses[0]
      # turn ["last_name DESC, first_name", "id"] into "last_name"
      order = order.split(", ")[0]
      
      operator = order =~ /desc/i ? '>' : '<'
      order_column = order.split(" ")[0].split(".").last
      
      where(
        "#{table_name}.#{order_column} #{operator} ?",
        current.send(order_column)
      ).
      reverse_order.
      limit(1)
    end
  end
  
  define_method :next do
    self.class.priority_order.next(self).first
  end
  
  define_method :previous do
    self.class.priority_order.previous(self).first
  end
end