Module: ActiveFedora::Associations::ClassMethods

Defined in:
lib/active_fedora/associations.rb

Instance Method Summary collapse

Instance Method Details

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

Specifies a one-to-one association with another class. This method should only be used if this class contains the foreign key.

Methods will be added for retrieval and query for a single associated object, for which this object holds an id:

association()

Returns the associated object. nil is returned if none is found.

association=(associate)

Assigns the associate object, extracts the primary key, and sets it as the foreign key.

(association is replaced with the symbol passed as the first argument, so belongs_to :author would add among others author.nil?.)

Example

A Post class declares belongs_to :author, which will add:

  • Post#author (similar to Author.find(author_id))

  • Post#author=(author)

The declaration can also include an options hash to specialize the behavior of the association.

Options

:predicate

the association predicate to use when storing the association REQUIRED

:class_name

Specify the class name of the association. Use it only if that name can't be inferred from the association name. So has_one :author will by default be linked to the Author class, but if the real class name is Person, you'll have to specify it with this option.

Option examples:

belongs_to :firm, predicate: OurVocab.clientOf
belongs_to :author, class_name: "Person", predicate: OurVocab.authorOf

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# File 'lib/active_fedora/associations.rb', line 134

def belongs_to(name, options = {})
  Builder::BelongsTo.build(self, name, options)

  Builder::SingularProperty.build(self, name, options)
end

#contains(name, options = {}) { ... } ⇒ Object

This method is used to specify the details of a contained resource. Pass the name as the first argument and a hash of options as the second argument Note that this method doesn't actually execute the block, but stores it, to be executed by any the implementation of the datastream(specified as :class_name)

Options Hash (options):

  • :class_name (Class)

    The class that will represent this child, should extend “ActiveFedora::File''

  • :url (String)
  • :autocreate (Boolean)

    Always create this datastream on new objects

Yields:

  • block executed by some types of child resources

Raises:

  • (ArgumentError)

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# File 'lib/active_fedora/associations.rb', line 95

def contains(name, options = {}, &block)
  options[:block] = block if block
  raise ArgumentError, "You must provide a name (dsid) for the datastream" unless name
  Associations::Builder::Contains.build(self, name.to_sym, options)
end

#has_and_belongs_to_many(name, options = {}) ⇒ Object

Specifies a many-to-many relationship with another class. The relatioship is written to both classes simultaneously.

Adds the following methods for retrieval and query:

collection(force_reload = false)

Returns an array of all the associated objects. An empty array is returned if none are found.

collection<<(object, …)

Adds one or more objects to the collection by creating associations in the join table (collection.push and collection.concat are aliases to this method). Note that this operation instantly fires update sql without waiting for the save or update call on the parent object.

collection.delete(object, …)

Removes one or more objects from the collection by removing their associations from the join table. This does not destroy the objects.

collection=objects

Replaces the collection's content by deleting and adding objects as appropriate.

collection_singular_ids

Returns an array of the associated objects' ids.

collection_singular_ids=ids

Replace the collection by the objects identified by the primary keys in ids.

collection.clear

Removes every object from the collection. This does not destroy the objects.

collection.empty?

Returns true if there are no associated objects.

collection.size

Returns the number of associated objects.

(collection is replaced with the symbol passed as the first argument, so has_and_belongs_to_many :categories would add among others categories.empty?.)

Example

A Developer class declares has_and_belongs_to_many :projects, which will add:

  • Developer#projects

  • Developer#projects<<

  • Developer#projects.delete

  • Developer#projects=

  • Developer#project_ids

  • Developer#project_ids=

  • Developer#projects.clear

  • Developer#projects.empty?

  • Developer#projects.size

  • Developer#projects.find(id)

  • Developer#projects.exists?(...)

The declaration may include an options hash to specialize the behavior of the association.

Options

:class_name

Specify the class name of the association. Use it only if that name can't be inferred from the association name. So has_and_belongs_to_many :projects will by default be linked to the Project class, but if the real class name is SuperProject, you'll have to specify it with this option.

:predicate

REQUIRED Specify the predicate to use when storing the relationship.

:inverse_of

Specify the predicate to use when storing the relationship on the foreign object. If it is not provided, the relationship will not set the foriegn association.

Option examples:

has_and_belongs_to_many :projects, predicate: OurVocab.worksOn
has_and_belongs_to_many :nations, class_name: "Country", predicate: OurVocab.isCitizenOf
has_and_belongs_to_many :topics, predicate: RDF::FOAF.isPrimaryTopicOf, inverse_of: :is_topic_of

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# File 'lib/active_fedora/associations.rb', line 203

def has_and_belongs_to_many(name, options = {})
  Builder::HasAndBelongsToMany.build(self, name, options)
  Builder::Property.build(self, name, options.slice(:class_name, :predicate))
end

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


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# File 'lib/active_fedora/associations.rb', line 80

def has_many(name, options={})
  Builder::HasMany.build(self, name, options)
end