Class: Momomoto::Order

Inherits:
Object
  • Object
show all
Defined in:
lib/momomoto/order.rb

Overview

This class is used to specify the order of returned Rows. Whenever selecting rows you can use plain Symbols for column names or the builtin classes for having the result automatically sorted asc ending, descending or case-insensitive with lower.

When executing SELECT on tables the method Base#compile_order is invoked, which compiles the order statement according to Table#default_order if defined. This can be overwritten with options set as parameter for the select method.

class Feeds < Momomoto::Table
  default_order Momomoto.desc( :last_changed )
  #equals default_order Momomoto::Order::Desc.new( :last_changed )
end

newest_five_feeds = Feeds.select( {}, { :limit => 5} )
  => Returns the five rows from Feeds with the newest column last_changed

Now, if you want to get all feeds sorted by column title instead of last_changed and also want to ignore case, do the following:

feeds_by_title = Feeds.select( {}, {:order => Momomoto::lower(:title)} )

This overwrites the default value for order.

You can also define multiple order statements at once, which are then joined together.

class Feeds < Momomoto::Table
  default_order [Momomoto::desc(:last_changed), Momomoto::lower(:title)]
end

Direct Known Subclasses

Asc, Desc, Lower

Defined Under Namespace

Classes: Asc, Desc, Lower

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*fields) ⇒ Order

Creates a new instance of Order and flattens the given parameter fields.

Usage:

Momomoto::Order.new(:url_class, [:url, :title])



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# File 'lib/momomoto/order.rb', line 46

def initialize( *fields )
  @fields = fields.flatten
end

Instance Attribute Details

#fields ⇒ Object

Getter and setter methods for fields. fields are Symbols representing the columns the Order class operates on.



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# File 'lib/momomoto/order.rb', line 39

def fields
  @fields
end

Instance Method Details

#to_sql(columns) ⇒ Object

This method is used to build the SQL statement from the given columns and their class. This method is only invoked from Base#compile_order.



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# File 'lib/momomoto/order.rb', line 53

def to_sql( columns )
  sql = []
  fields.each do | field |
    if field.kind_of?( Momomoto::Order )
      sql << function( field.to_sql( columns ) )
    else
      raise Momomoto::Error, "Unknown field #{field} in order" if not columns.keys.member?( field.to_sym )
      sql << function( field  )
    end
  end
  sql.join(',')
end