Module | Sequel::Model::Associations::ClassMethods |
In: |
lib/sequel/model/associations.rb
|
Each kind of association adds a number of instance methods to the model class which are specialized according to the association type and optional parameters given in the definition. Example:
class Project < Sequel::Model many_to_one :portfolio # or: one_to_one :portfolio one_to_many :milestones # or: many_to_many :milestones end
The project class now has the following instance methods:
portfolio : | Returns the associated portfolio. |
portfolio=(obj) : | Sets the associated portfolio to the object, but the change is not persisted until you save the record (for many_to_one associations). |
portfolio_dataset : | Returns a dataset that would return the associated portfolio, only useful in fairly specific circumstances. |
milestones : | Returns an array of associated milestones |
add_milestone(obj) : | Associates the passed milestone with this object. |
remove_milestone(obj) : | Removes the association with the passed milestone. |
remove_all_milestones : | Removes associations with all associated milestones. |
milestones_dataset : | Returns a dataset that would return the associated milestones, allowing for further filtering/limiting/etc. |
If you want to override the behavior of the add_/remove_/remove_all_/ methods or the association setter method, there are private instance methods created that are prepended with an underscore (e.g. _add_milestone or _portfolio=). The private instance methods can be easily overridden, but you shouldn‘t override the public instance methods without calling super, as they deal with callbacks and caching.
By default the classes for the associations are inferred from the association name, so for example the Project#portfolio will return an instance of Portfolio, and Project#milestones will return an array of Milestone instances. You can use the :class option to change which class is used.
Association definitions are also reflected by the class, e.g.:
Project.associations => [:portfolio, :milestones] Project.association_reflection(:portfolio) => {:type => :many_to_one, :name => :portfolio, ...}
For a more in depth general overview, as well as a reference guide, see the Association Basics guide. For examples of advanced usage, see the Advanced Associations guide.
association_reflections | [R] | All association reflections defined for this model (default: {}). |
Associates a related model with the current model. The following types are supported:
The following options can be supplied:
# File lib/sequel/model/associations.rb, line 626 626: def associate(type, name, opts = {}, &block) 627: raise(Error, 'one_to_many association type with :one_to_one option removed, used one_to_one association type') if opts[:one_to_one] && type == :one_to_many 628: raise(Error, 'invalid association type') unless assoc_class = ASSOCIATION_TYPES[type] 629: raise(Error, 'Model.associate name argument must be a symbol') unless Symbol === name 630: raise(Error, ':eager_loader option must have an arity of 1 or 3') if opts[:eager_loader] && ![1, 3].include?(opts[:eager_loader].arity) 631: 632: # dup early so we don't modify opts 633: orig_opts = opts.dup 634: orig_opts = association_reflection(opts[:clone])[:orig_opts].merge(orig_opts) if opts[:clone] 635: opts = orig_opts.merge(:type => type, :name => name, :cache => true, :model => self) 636: opts[:block] = block if block 637: opts = assoc_class.new.merge!(opts) 638: opts[:eager_block] = block unless opts.include?(:eager_block) 639: opts[:graph_join_type] ||= :left_outer 640: opts[:order_eager_graph] = true unless opts.include?(:order_eager_graph) 641: conds = opts[:conditions] 642: opts[:graph_conditions] = conds if !opts.include?(:graph_conditions) and Sequel.condition_specifier?(conds) 643: opts[:graph_conditions] = opts.fetch(:graph_conditions, []).to_a 644: opts[:graph_select] = Array(opts[:graph_select]) if opts[:graph_select] 645: [:before_add, :before_remove, :after_add, :after_remove, :after_load, :before_set, :after_set, :extend].each do |cb_type| 646: opts[cb_type] = Array(opts[cb_type]) 647: end 648: late_binding_class_option(opts, opts.returns_array? ? singularize(name) : name) 649: 650: send("def_#{type}""def_#{type}", opts) 651: 652: orig_opts.delete(:clone) 653: orig_opts.merge!(:class_name=>opts[:class_name], :class=>opts[:class], :block=>block) 654: opts[:orig_opts] = orig_opts 655: # don't add to association_reflections until we are sure there are no errors 656: association_reflections[name] = opts 657: end
The association reflection hash for the association of the given name.
# File lib/sequel/model/associations.rb, line 660 660: def association_reflection(name) 661: association_reflections[name] 662: end
Modify and return eager loading dataset based on association options.
# File lib/sequel/model/associations.rb, line 670 670: def eager_loading_dataset(opts, ds, select, associations, eager_options={}) 671: ds = ds.select(*select) if select 672: if c = opts[:conditions] 673: ds = (c.is_a?(Array) && !Sequel.condition_specifier?(c)) ? ds.filter(*c) : ds.filter(c) 674: end 675: ds = ds.order(*opts[:order]) if opts[:order] 676: ds = ds.eager(opts[:eager]) if opts[:eager] 677: ds = ds.distinct if opts[:distinct] 678: if opts[:eager_graph] 679: ds = ds.eager_graph(opts[:eager_graph]) 680: ds = ds.add_graph_aliases(opts.associated_key_alias=>[opts.associated_class.table_name, opts.associated_key_alias, SQL::QualifiedIdentifier.new(opts.associated_key_table, opts.associated_key_column)]) if opts.eager_loading_use_associated_key? 681: elsif opts.eager_loading_use_associated_key? 682: ds = if opts[:uses_left_composite_keys] 683: t = opts.associated_key_table 684: ds.select_more(*opts.associated_key_alias.zip(opts.associated_key_column).map{|a, c| SQL::AliasedExpression.new(SQL::QualifiedIdentifier.new(t, c), a)}) 685: else 686: ds.select_more(SQL::AliasedExpression.new(SQL::QualifiedIdentifier.new(opts.associated_key_table, opts.associated_key_column), opts.associated_key_alias)) 687: end 688: end 689: ds = ds.eager(associations) unless Array(associations).empty? 690: ds = opts[:eager_block].call(ds) if opts[:eager_block] 691: ds 692: end
Copy the association reflections to the subclass
# File lib/sequel/model/associations.rb, line 695 695: def inherited(subclass) 696: super 697: subclass.instance_variable_set(:@association_reflections, @association_reflections.dup) 698: end
Shortcut for adding a many_to_many association, see associate
# File lib/sequel/model/associations.rb, line 701 701: def many_to_many(name, opts={}, &block) 702: associate(:many_to_many, name, opts, &block) 703: end
Shortcut for adding a many_to_one association, see associate
# File lib/sequel/model/associations.rb, line 706 706: def many_to_one(name, opts={}, &block) 707: associate(:many_to_one, name, opts, &block) 708: end
Shortcut for adding a one_to_many association, see associate
# File lib/sequel/model/associations.rb, line 711 711: def one_to_many(name, opts={}, &block) 712: associate(:one_to_many, name, opts, &block) 713: end
Shortcut for adding a one_to_one association, see associate.
# File lib/sequel/model/associations.rb, line 716 716: def one_to_one(name, opts={}, &block) 717: associate(:one_to_one, name, opts, &block) 718: end