Module: Sequel::Model::Associations::ClassMethods

Defined in:
lib/sequel/model/associations.rb

Overview

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, ...}

Associations should not have the same names as any of the columns in the model’s current table they reference. If you are dealing with an existing schema that has a column named status, you can’t name the association status, you’d have to name it foo_status or something else. If you give an association the same name as a column, you will probably end up with an association that doesn’t work, or a SystemStackError.

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.

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#association_reflections ⇒ Object (readonly)

All association reflections defined for this model (default: {}).



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# File 'lib/sequel/model/associations.rb', line 666

def association_reflections
  @association_reflections
end

#default_eager_limit_strategy ⇒ Object

The default :eager_limit_strategy option to use for *_many associations (default: nil)



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# File 'lib/sequel/model/associations.rb', line 669

def default_eager_limit_strategy
  @default_eager_limit_strategy
end

Instance Method Details

#all_association_reflections ⇒ Object

Array of all association reflections for this model class



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# File 'lib/sequel/model/associations.rb', line 672

def all_association_reflections
  association_reflections.values
end

#apply_association_dataset_opts(opts, ds) ⇒ Object

Given an association reflection and a dataset, apply the :select, :conditions, :order, :eager, :distinct, and :eager_block association options to the given dataset and return the dataset or a modified copy of it.



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# File 'lib/sequel/model/associations.rb', line 680

def apply_association_dataset_opts(opts, ds)
  ds = ds.select(*opts.select) if opts.select
  if c = opts[:conditions]
    ds = (c.is_a?(Array) && !Sequel.condition_specifier?(c)) ? ds.filter(*c) : ds.filter(c)
  end
  ds = ds.order(*opts[:order]) if opts[:order]
  ds = ds.eager(opts[:eager]) if opts[:eager]
  ds = ds.distinct if opts[:distinct]
  ds = opts[:eager_block].call(ds) if opts[:eager_block]
  ds
end

#associate(type, name, opts = {}, &block) ⇒ Object

Associates a related model with the current model. The following types are supported:

:many_to_one

Foreign key in current model’s table points to associated model’s primary key. Each associated model object can be associated with more than one current model objects. Each current model object can be associated with only one associated model object.

:one_to_many

Foreign key in associated model’s table points to this model’s primary key. Each current model object can be associated with more than one associated model objects. Each associated model object can be associated with only one current model object.

:one_to_one

Similar to one_to_many in terms of foreign keys, but only one object is associated to the current object through the association. The methods created are similar to many_to_one, except that the one_to_one setter method saves the passed object.

:many_to_many

A join table is used that has a foreign key that points to this model’s primary key and a foreign key that points to the associated model’s primary key. Each current model object can be associated with many associated model objects, and each associated model object can be associated with many current model objects.

The following options can be supplied:

All Types

:after_add

Symbol, Proc, or array of both/either specifying a callback to call after a new item is added to the association.

:after_load

Symbol, Proc, or array of both/either specifying a callback to call after the associated record(s) have been retrieved from the database.

:after_remove

Symbol, Proc, or array of both/either specifying a callback to call after an item is removed from the association.

:after_set

Symbol, Proc, or array of both/either specifying a callback to call after an item is set using the association setter method.

:allow_eager

If set to false, you cannot load the association eagerly via eager or eager_graph

:before_add

Symbol, Proc, or array of both/either specifying a callback to call before a new item is added to the association.

:before_remove

Symbol, Proc, or array of both/either specifying a callback to call before an item is removed from the association.

:before_set

Symbol, Proc, or array of both/either specifying a callback to call before an item is set using the association setter method.

:cartesian_product_number

the number of joins completed by this association that could cause more than one row for each row in the current table (default: 0 for many_to_one and one_to_one associations, 1 for one_to_many and many_to_many associations).

:class

The associated class or its name. If not given, uses the association’s name, which is camelized (and singularized unless the type is :many_to_one or :one_to_one)

:clone

Merge the current options and block into the options and block used in defining the given association. Can be used to DRY up a bunch of similar associations that all share the same options such as :class and :key, while changing the order and block used.

:conditions

The conditions to use to filter the association, can be any argument passed to filter.

:dataset

A proc that is instance_evaled to get the base dataset to use for the _dataset method (before the other options are applied).

:distinct

Use the DISTINCT clause when selecting associating object, both when lazy loading and eager loading via .eager (but not when using .eager_graph).

:eager

The associations to eagerly load via eager when loading the associated object(s).

:eager_block

If given, use the block instead of the default block when eagerly loading. To not use a block when eager loading (when one is used normally), set to nil.

:eager_graph

The associations to eagerly load via eager_graph when loading the associated object(s). many_to_many associations with this option cannot be eagerly loaded via eager.

:eager_grapher

A proc to use to implement eager loading via eager_graph, overriding the default. Takes one or three arguments. If three arguments, they are a dataset, an alias to use for the table to graph for this association, and the alias that was used for the current table (since you can cascade associations). If one argument, is passed a hash with keys :self, :table_alias, and :implicit_qualifier, corresponding to the three arguments, and an optional additional key :eager_block, a callback accepting one argument, the associated dataset. This is used to customize the association at query time. Should return a copy of the dataset with the association graphed into it.

:eager_limit_strategy

Determines the strategy used for enforcing limits when eager loading associations via the eager method. For one_to_one associations, no strategy is used by default, and for *_many associations, the :ruby strategy is used by default, which still retrieves all records but slices the resulting array after the association is retrieved. You can pass a true value for this option to have Sequel pick what it thinks is the best choice for the database, or specify a specific symbol to manually select a strategy. one_to_one associations support :distinct_on, :window_function, and :correlated_subquery. *_many associations support :ruby, :window_function, and :correlated_subquery.

:eager_loader

A proc to use to implement eager loading, overriding the default. Takes one or three arguments. If three arguments, the first should be a key hash (used solely to enhance performance), the second an array of records, and the third a hash of dependent associations. If one argument, is passed a hash with keys :key_hash, :rows, and :associations, corresponding to the three arguments, and an additional key :self, which is the dataset doing the eager loading. In the proc, the associated records should be queried from the database and the associations cache for each record should be populated.

:eager_loader_key

A symbol for the key column to use to populate the key hash for the eager loader.

:extend

A module or array of modules to extend the dataset with.

:graph_alias_base

The base name to use for the table alias when eager graphing. Defaults to the name of the association. If the alias name has already been used in the query, Sequel will create a unique alias by appending a numeric suffix (e.g. alias_0, alias_1, …) until the alias is unique.

:graph_block

The block to pass to join_table when eagerly loading the association via eager_graph.

:graph_conditions

The additional conditions to use on the SQL join when eagerly loading the association via eager_graph. Should be a hash or an array of two element arrays. If not specified, the :conditions option is used if it is a hash or array of two element arrays.

:graph_join_type

The type of SQL join to use when eagerly loading the association via eager_graph. Defaults to :left_outer.

:graph_only_conditions

The conditions to use on the SQL join when eagerly loading the association via eager_graph, instead of the default conditions specified by the foreign/primary keys. This option causes the :graph_conditions option to be ignored.

:graph_select

A column or array of columns to select from the associated table when eagerly loading the association via eager_graph. Defaults to all columns in the associated table.

:limit

Limit the number of records to the provided value. Use an array with two elements for the value to specify a limit (first element) and an offset (second element).

:methods_module

The module that methods the association creates will be placed into. Defaults to the module containing the model’s columns.

:order

the column(s) by which to order the association dataset. Can be a singular column symbol or an array of column symbols.

:order_eager_graph

Whether to add the association’s order to the graphed dataset’s order when graphing via eager_graph. Defaults to true, so set to false to disable.

:read_only

Do not add a setter method (for many_to_one or one_to_one associations), or add_/remove_/remove_all_ methods (for one_to_many and many_to_many associations).

:reciprocal

the symbol name of the reciprocal association, if it exists. By default, Sequel will try to determine it by looking at the associated model’s assocations for a association that matches the current association’s key(s). Set to nil to not use a reciprocal.

:select

the columns to select. Defaults to the associated class’s table_name.* in a many_to_many association, which means it doesn’t include the attributes from the join table. If you want to include the join table attributes, you can use this option, but beware that the join table attributes can clash with attributes from the model table, so you should alias any attributes that have the same name in both the join table and the associated table.

:validate

Set to false to not validate when implicitly saving any associated object.

:many_to_one

:key

foreign key in current model’s table that references associated model’s primary key, as a symbol. Defaults to :“#name_id”. Can use an array of symbols for a composite key association.

:key_column

Similar to, and usually identical to, :key, but :key refers to the model method to call, where :key_column refers to the underlying column. Should only be used if the the model method differs from the foreign key column, in conjunction with defining a model alias method for the key column.

:primary_key

column in the associated table that :key option references, as a symbol. Defaults to the primary key of the associated table. Can use an array of symbols for a composite key association.

:primary_key_method

the method symbol or array of method symbols to call on the associated object to get the foreign key values. Defaults to :primary_key option.

:qualify

Whether to use qualifier primary keys when loading the association. The default is true, so you must set to false to not qualify. Qualification rarely causes problems, but it’s necessary to disable in some cases, such as when you are doing a JOIN USING operation on the column on Oracle.

:one_to_many and :one_to_one

:key

foreign key in associated model’s table that references current model’s primary key, as a symbol. Defaults to :“#Sequel::Model::Associations::ClassMethods.selfself.nameself.name.underscore_id”. Can use an array of symbols for a composite key association.

:key_method

the method symbol or array of method symbols to call on the associated object to get the foreign key values. Defaults to :key option.

:primary_key

column in the current table that :key option references, as a symbol. Defaults to primary key of the current table. Can use an array of symbols for a composite key association.

:primary_key_column

Similar to, and usually identical to, :primary_key, but :primary_key refers to the model method call, where :primary_key_column refers to the underlying column. Should only be used if the the model method differs from the primary key column, in conjunction with defining a model alias method for the primary key column.

:many_to_many

:graph_join_table_block

The block to pass to join_table for the join table when eagerly loading the association via eager_graph.

:graph_join_table_conditions

The additional conditions to use on the SQL join for the join table when eagerly loading the association via eager_graph. Should be a hash or an array of two element arrays.

:graph_join_table_join_type

The type of SQL join to use for the join table when eagerly loading the association via eager_graph. Defaults to the :graph_join_type option or :left_outer.

:graph_join_table_only_conditions

The conditions to use on the SQL join for the join table when eagerly loading the association via eager_graph, instead of the default conditions specified by the foreign/primary keys. This option causes the :graph_join_table_conditions option to be ignored.

:join_table

name of table that includes the foreign keys to both the current model and the associated model, as a symbol. Defaults to the name of current model and name of associated model, pluralized, underscored, sorted, and joined with ‘_’.

:join_table_block

proc that can be used to modify the dataset used in the add/remove/remove_all methods. Should accept a dataset argument and return a modified dataset if present.

:left_key

foreign key in join table that points to current model’s primary key, as a symbol. Defaults to :“#Sequel::Model::Associations::ClassMethods.selfself.nameself.name.underscore_id”. Can use an array of symbols for a composite key association.

:left_primary_key

column in current table that :left_key points to, as a symbol. Defaults to primary key of current table. Can use an array of symbols for a composite key association.

:left_primary_key_column

Similar to, and usually identical to, :left_primary_key, but :left_primary_key refers to the model method to call, where :left_primary_key_column refers to the underlying column. Should only be used if the model method differs from the left primary key column, in conjunction with defining a model alias method for the left primary key column.

:right_key

foreign key in join table that points to associated model’s primary key, as a symbol. Defaults to :“#Sequel::Model::Associations::ClassMethods.namename.to_sname.to_s.singularize_id”. Can use an array of symbols for a composite key association.

:right_primary_key

column in associated table that :right_key points to, as a symbol. Defaults to primary key of the associated table. Can use an array of symbols for a composite key association.

:right_primary_key_method

the method symbol or array of method symbols to call on the associated object to get the foreign key values for the join table. Defaults to :right_primary_key option.

:uniq

Adds a after_load callback that makes the array of objects unique.

Raises:



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# File 'lib/sequel/model/associations.rb', line 888

def associate(type, name, opts = {}, &block)
  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
  raise(Error, 'invalid association type') unless assoc_class = ASSOCIATION_TYPES[type]
  raise(Error, 'Model.associate name argument must be a symbol') unless Symbol === name
  raise(Error, ':eager_loader option must have an arity of 1 or 3') if opts[:eager_loader] && ![1, 3].include?(opts[:eager_loader].arity)
  raise(Error, ':eager_grapher option must have an arity of 1 or 3') if opts[:eager_grapher] && ![1, 3].include?(opts[:eager_grapher].arity)

  # dup early so we don't modify opts
  orig_opts = opts.dup
  orig_opts = association_reflection(opts[:clone])[:orig_opts].merge(orig_opts) if opts[:clone]
  opts = orig_opts.merge(:type => type, :name => name, :cache=>{}, :model => self)
  opts[:block] = block if block
  opts = assoc_class.new.merge!(opts)
  opts[:eager_block] = block unless opts.include?(:eager_block)
  opts[:graph_join_type] ||= :left_outer
  opts[:order_eager_graph] = true unless opts.include?(:order_eager_graph)
  conds = opts[:conditions]
  opts[:graph_alias_base] ||= name
  opts[:graph_conditions] = conds if !opts.include?(:graph_conditions) and Sequel.condition_specifier?(conds)
  opts[:graph_conditions] = opts.fetch(:graph_conditions, []).to_a
  opts[:graph_select] = Array(opts[:graph_select]) if opts[:graph_select]
  [:before_add, :before_remove, :after_add, :after_remove, :after_load, :before_set, :after_set, :extend].each do |cb_type|
    opts[cb_type] = Array(opts[cb_type])
  end
  late_binding_class_option(opts, opts.returns_array? ? singularize(name) : name)
  
  # Remove :class entry if it exists and is nil, to work with cached_fetch
  opts.delete(:class) unless opts[:class]
  
  send(:"def_#{type}", opts)
      
  orig_opts.delete(:clone)
  orig_opts.merge!(:class_name=>opts[:class_name], :class=>opts[:class], :block=>block)
  opts[:orig_opts] = orig_opts
  # don't add to association_reflections until we are sure there are no errors
  association_reflections[name] = opts
end

#association_reflection(name) ⇒ Object

The association reflection hash for the association of the given name.



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# File 'lib/sequel/model/associations.rb', line 927

def association_reflection(name)
  association_reflections[name]
end

#associations ⇒ Object

Array of association name symbols



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# File 'lib/sequel/model/associations.rb', line 932

def associations
  association_reflections.keys
end

#eager_loading_dataset(opts, ds, select, associations, eager_options = {}) ⇒ Object

Modify and return eager loading dataset based on association options.



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# File 'lib/sequel/model/associations.rb', line 937

def eager_loading_dataset(opts, ds, select, associations, eager_options={})
  ds = apply_association_dataset_opts(opts, ds)
  ds = ds.select(*select) if select
  if opts[:eager_graph]
    raise(Error, "cannot eagerly load a #{opts[:type]} association that uses :eager_graph") if opts.eager_loading_use_associated_key?
    ds = ds.eager_graph(opts[:eager_graph])
  end
  ds = ds.eager(associations) unless Array(associations).empty?
  ds = eager_options[:eager_block].call(ds) if eager_options[:eager_block]
  if opts.eager_loading_use_associated_key?
    ds = if opts[:uses_left_composite_keys]
      ds.select_append(*opts.associated_key_alias.zip(opts.eager_loading_predicate_key).map{|a, k| SQL::AliasedExpression.new(k, a)})
    else
      ds.select_append(SQL::AliasedExpression.new(opts.eager_loading_predicate_key, opts.associated_key_alias))
    end
  end
  ds
end

#inherited(subclass) ⇒ Object

Copy the association reflections to the subclass



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# File 'lib/sequel/model/associations.rb', line 957

def inherited(subclass)
  super
  subclass.instance_variable_set(:@association_reflections, association_reflections.dup)
  subclass.default_eager_limit_strategy =  default_eager_limit_strategy
end

#many_to_many(name, opts = {}, &block) ⇒ Object

Shortcut for adding a many_to_many association, see #associate



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# File 'lib/sequel/model/associations.rb', line 964

def many_to_many(name, opts={}, &block)
  associate(:many_to_many, name, opts, &block)
end

#many_to_one(name, opts = {}, &block) ⇒ Object

Shortcut for adding a many_to_one association, see #associate



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# File 'lib/sequel/model/associations.rb', line 969

def many_to_one(name, opts={}, &block)
  associate(:many_to_one, name, opts, &block)
end

#one_to_many(name, opts = {}, &block) ⇒ Object

Shortcut for adding a one_to_many association, see #associate



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# File 'lib/sequel/model/associations.rb', line 974

def one_to_many(name, opts={}, &block)
  associate(:one_to_many, name, opts, &block)
end

#one_to_one(name, opts = {}, &block) ⇒ Object

Shortcut for adding a one_to_one association, see #associate.



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# File 'lib/sequel/model/associations.rb', line 979

def one_to_one(name, opts={}, &block)
  associate(:one_to_one, name, opts, &block)
end