Module: Og::MetaLanguage

Included in:
Module
Defined in:
lib/og/meta.rb

Overview

Implements a meta-language for manipulating og-managed objects and defining their relationships. The original idea comes from the excellent ActiveRecord library.

Many more useful relations will be available soon.

Instance Method Summary collapse

Instance Method Details

#belongs_to(name, klass, options = {}) ⇒ Object

Implements a ‘belongs_to’ relation. Automatically enchants the calling class with helper methods.

Example:

class MyObject belongs_to AnotherObject, :prop => :parent end

creates the code:

prop_accessor Fixnum, :parent_oid def parent; … end def parent=(obj_or_oid); … end



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# File 'lib/og/meta.rb', line 84

def belongs_to(name, klass, options = {})
	prop_eval = "prop_accessor Fixnum, :#{name}_oid"
	prop_eval << ", :sql => '#{options[:sql]}'" if options[:sql]
	prop_eval << ", :extra_sql => '#{options[:extra_sql]}'" if options[:extra_sql]

	meta :belongs_to, klass
	
	module_eval %{
		#{prop_eval}
		
		def #{name}
			Og.db.load_by_oid(@#{name}_oid, #{klass})
		end
		
		def #{name}=(obj_or_oid)
			@#{name}_oid = obj_or_oid.to_i
		end
	}
end

#has_many(name, klass, options = {}) ⇒ Object

Implements a ‘has_many’ relation. Automatically enchants the calling class with helper methods.

Example:

class MyObject has_many :children, AnotherObject end

creates the code:

def children; … end



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# File 'lib/og/meta.rb', line 151

def has_many(name, klass, options = {})
	name_s = N::Inflector.singularize(name.to_s)
	
	# linkback is the property of the child object that 'links back' 
	# to this object. 

	linkback = options[:linkback] || "#{MetaUtils.expand(self)}_oid"
	
	# keep belongs to metadata, useful for 
	# reflection/scaffolding.

	meta :has, [klass, linkback]

	module_eval %{
		def #{name}(extrasql = nil)
			Og.db.select("SELECT * FROM #{Og::Adapter.table(klass)} WHERE #{linkback}=\#\@oid \#\{extrasql\}", #{klass})
		end

		def #{name}_count(extrasql = nil)
			Og.db.count("SELECT COUNT(*) FROM #{Og::Adapter.table(klass)} WHERE #{linkback}=\#\@oid \#\{extrasql\}")
		end			

		def add_#{name_s}(obj, extra = nil)
			obj.#{linkback} = @oid
			obj.save!
		end
		
		def delete_all_#{name}(extrasql = nil)
			Og.db.exec("DELETE FROM #{Og::Adapter.table(klass)} WHERE #{linkback}=\#\@oid \#\{extrasql\}") 
		end			
	}
end

#has_one(name, klass = nil, options = {}) ⇒ Object

Implements a ‘has_one’ relation. Automatically enchants the calling class with helper methods.

Example:

class MyObject has_one :child, TheClass has_one :article end

creates the code:

…



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# File 'lib/og/meta.rb', line 118

def has_one(name, klass = nil, options = {})

	# linkback is the property of the child object that 'links back' 
	# to this object. 

	linkback = options[:linkback] || "#{MetaUtils.expand(self)}_oid"
	
	meta :has, [klass, linkback]
	
	module_eval %{
		def #{name}(extrasql = nil)
			Og.db.select_one("SELECT * FROM #{Og::Adapter.table(klass)} WHERE #{linkback}=\#\@oid \#\{extrasql\}", #{klass})
		end

		def delete_#{name}(extrasql = nil)
			Og.db.exec("DELETE FROM #{Og::Adapter.table(klass)} WHERE #{linkback}=\#\@oid \#\{extrasql\}") 
		end			
	}
end

#joins(klass, options = {}) ⇒ Object

Declares that this class can join with another class. The join parameters are given so the join-compatible methods are generated.



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# File 'lib/og/meta.rb', line 323

def joins(klass, options = {})
	meta :joins, [klass, options]
end

#many_to_many(name, klass, options = {}) ⇒ Object Also known as: has_and_belongs_to_many

Implements a ‘many_to_many’ relation. Two objects are associated using an intermediate join table. Automatically enchants the calling class with helper methods.

Options:

Example:

class Article many_to_many :categories, Category, :linkback => articles end

article.categories article.del_category article.add_category article.clear_categories

category.articles … – FIXME: make more compatible with other enchant methods. ++



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# File 'lib/og/meta.rb', line 207

def many_to_many(name, klass, options = {})
	list_o = name.to_s
	prop_o = N::Inflector.singularize(list_o)
	list_m = options[:linkback] || N::Inflector.plural_name(self) 
	prop_m = N::Inflector.singularize(list_m)

	# exit if the class is allready indirectly 'enchanted' from the
	# other class of the many_to_many relation.

	return if self.respond_to?(prop_m)

	# Add some metadata to the class to allow for automatic join table
	# calculation.

	meta :sql_join, [klass, options]

	meta :many_to_many, klass
	klass.meta :many_to_many, self 

	# enchant this class
	
	module_eval %{
		def #{list_o}(extrasql = nil)
			Og.db.select("SELECT d.* FROM #{Og::Adapter.table(klass)} AS d, #{Og::Adapter.join_table(self, klass)} AS j WHERE j.key1=\#\@oid AND j.key2=d.oid \#\{extrasql\}", #{klass})
		end

		def #{list_o}_count(extrasql = nil)
			Og.db.select("SELECT COUNT(*) FROM #{Og::Adapter.table(klass)} AS d, #{Og::Adapter.join_table(self, klass)} AS j WHERE j.key1=\#\@oid AND j.key2=d.oid \#\{extrasql\}", #{klass})
		end						
		
		def add_#{prop_o}(obj, extra = nil)
			Og.db.exec("INSERT INTO #{Og::Adapter.join_table(self, klass)} (key1, key2) VALUES (\#\@oid, \#\{obj.oid\})") 
		end
		
		def delete_#{prop_o}(obj_or_oid, extra = nil)
			Og.db.exec("DELETE FROM #{Og::Adapter.join_table(self, klass)} WHERE key2=\#\{obj_or_oid.to_i\}") 
		end

		def clear_#{list_o}
			Og.db.exec("DELETE FROM #{Og::Adapter.join_table(self, klass)} WHERE key1=\#\@oid") 
		end			
	}
	
	# indirectly enchant the other class of the relation.
	
	klass.module_eval %{
		def #{list_m}(extrasql = nil)
			Og.db.select("SELECT s.* FROM #{Og::Adapter.table(self)} AS s, #{Og::Adapter.join_table(self, klass)} AS j WHERE j.key2=\#\@oid AND j.key1=s.oid \#\{extrasql\}", #{self})
		end

		def #{list_m}_count(extrasql = nil)
			Og.db.select("SELECT COUNT(*) FROM #{Og::Adapter.table(self)} AS s, #{Og::Adapter.join_table(self, klass)} AS j WHERE j.key2=\#\@oid AND j.key1=s.oid \#\{extrasql\}", #{self})
		end
		
		def add_#{prop_m}(obj, extra = nil)
			Og.db.exec("INSERT INTO #{Og::Adapter.join_table(self, klass)} (key1, key2) VALUES (\#\{obj.oid\}, \#\@oid)") 
		end
		
		def delete_#{prop_m}(obj_or_oid, extra = nil)
			Og.db.exec("DELETE FROM #{Og::Adapter.join_table(self, klass)} WHERE key1=\#\{obj_or_oid.to_i\}") 
		end

		def clear_#{list_m}
			Og.db.exec("DELETE FROM #{Og::Adapter.join_table(self, klass)} WHERE key2=\#\@oid") 
		end			
	}
end

#refers_to(name, klass, options = {}) ⇒ Object

Implements a ‘refers_to’ relation. This is a one-way version of the ‘has_one’/‘belongs_to’ relations. The target object cannot link back to the source object. This is in fact EXACTLY the same as belongs_to with a different name (!!!!)

Automatically enchants the calling class with helper methods.

Example:

class MyObject refers_to article, Article end

creates the code:

prop_accessor Fixnum, :article_oid def article; … end def article=(obj_or_oid); … end



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# File 'lib/og/meta.rb', line 298

def refers_to(name, klass, options = {})
	prop_eval = "prop_accessor Fixnum, :#{name}_oid"
	prop_eval << ", :sql => '#{options[:sql]}'" if options[:sql]
	prop_eval << ", :extra_sql => '#{options[:extra_sql]}'" if options[:extra_sql]

	meta :refers_to, klass
	klass.meta :has, [self, "#{name}_oid"]
	
	module_eval %{
		#{prop_eval}
		
		def #{name}
			Og.db.load_by_oid(@#{name}_oid, #{klass})
		end
		
		def #{name}=(obj_or_oid)
			@#{name}_oid = obj_or_oid.to_i
		end
	}
end

#sql_index(index, options = {}) ⇒ Object

Defines an SQL index. Useful for defining indiced over multiple columns.



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# File 'lib/og/meta.rb', line 65

def sql_index(index, options = {})
	meta :sql_index, [index, options]
end