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, :class_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: none). |
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 619 619: def associate(type, name, opts = {}, &block) 620: 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 621: raise(Error, 'invalid association type') unless assoc_class = ASSOCIATION_TYPES[type] 622: raise(Error, 'Model.associate name argument must be a symbol') unless Symbol === name 623: raise(Error, ':eager_loader option must have an arity of 1 or 3') if opts[:eager_loader] && ![1, 3].include?(opts[:eager_loader].arity) 624: 625: # merge early so we don't modify opts 626: orig_opts = opts.dup 627: orig_opts = association_reflection(opts[:clone])[:orig_opts].merge(orig_opts) if opts[:clone] 628: opts = orig_opts.merge(:type => type, :name => name, :cache => true, :model => self) 629: opts[:block] = block if block 630: opts = assoc_class.new.merge!(opts) 631: opts[:eager_block] = block unless opts.include?(:eager_block) 632: opts[:graph_join_type] ||= :left_outer 633: opts[:order_eager_graph] = true unless opts.include?(:order_eager_graph) 634: conds = opts[:conditions] 635: opts[:graph_conditions] = conds if !opts.include?(:graph_conditions) and Sequel.condition_specifier?(conds) 636: opts[:graph_conditions] = opts.fetch(:graph_conditions, []).to_a 637: opts[:graph_select] = Array(opts[:graph_select]) if opts[:graph_select] 638: [:before_add, :before_remove, :after_add, :after_remove, :after_load, :before_set, :after_set, :extend].each do |cb_type| 639: opts[cb_type] = Array(opts[cb_type]) 640: end 641: late_binding_class_option(opts, opts.returns_array? ? singularize(name) : name) 642: 643: send("def_#{type}""def_#{type}", opts) 644: 645: orig_opts.delete(:clone) 646: orig_opts.merge!(:class_name=>opts[:class_name], :class=>opts[:class], :block=>block) 647: opts[:orig_opts] = orig_opts 648: # don't add to association_reflections until we are sure there are no errors 649: association_reflections[name] = opts 650: end
The association reflection hash for the association of the given name.
# File lib/sequel/model/associations.rb, line 653 653: def association_reflection(name) 654: association_reflections[name] 655: end
Modify and return eager loading dataset based on association options. Options:
# File lib/sequel/model/associations.rb, line 663 663: def eager_loading_dataset(opts, ds, select, associations, eager_options={}) 664: ds = ds.select(*select) if select 665: if c = opts[:conditions] 666: ds = (c.is_a?(Array) && !Sequel.condition_specifier?(c)) ? ds.filter(*c) : ds.filter(c) 667: end 668: ds = ds.order(*opts[:order]) if opts[:order] 669: ds = ds.eager(opts[:eager]) if opts[:eager] 670: ds = ds.distinct if opts[:distinct] 671: if opts[:eager_graph] 672: ds = ds.eager_graph(opts[:eager_graph]) 673: 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? 674: elsif opts.eager_loading_use_associated_key? 675: ds = if opts[:uses_left_composite_keys] 676: t = opts.associated_key_table 677: ds.select_more(*opts.associated_key_alias.zip(opts.associated_key_column).map{|a, c| SQL::AliasedExpression.new(SQL::QualifiedIdentifier.new(t, c), a)}) 678: else 679: ds.select_more(SQL::AliasedExpression.new(SQL::QualifiedIdentifier.new(opts.associated_key_table, opts.associated_key_column), opts.associated_key_alias)) 680: end 681: end 682: ds = ds.eager(associations) unless Array(associations).empty? 683: ds = opts[:eager_block].call(ds) if opts[:eager_block] 684: ds 685: end
Copy the association reflections to the subclass
# File lib/sequel/model/associations.rb, line 688 688: def inherited(subclass) 689: super 690: subclass.instance_variable_set(:@association_reflections, @association_reflections.dup) 691: end
Shortcut for adding a many_to_many association, see associate
# File lib/sequel/model/associations.rb, line 694 694: def many_to_many(name, opts={}, &block) 695: associate(:many_to_many, name, opts, &block) 696: end
Shortcut for adding a many_to_one association, see associate
# File lib/sequel/model/associations.rb, line 699 699: def many_to_one(name, opts={}, &block) 700: associate(:many_to_one, name, opts, &block) 701: end
Shortcut for adding a one_to_many association, see associate
# File lib/sequel/model/associations.rb, line 704 704: def one_to_many(name, opts={}, &block) 705: associate(:one_to_many, name, opts, &block) 706: end
Shortcut for adding a one_to_one association, see associate.
# File lib/sequel/model/associations.rb, line 709 709: def one_to_one(name, opts={}, &block) 710: associate(:one_to_one, name, opts, &block) 711: end