Class: Prim::Relationship

Inherits:
Object
  • Object
show all
Defined in:
lib/prim/relationship.rb

Overview

This class largely wraps ActiveRecord::Reflection::MacroReflection and its subclasses. A Relationship encapsulates the interaction among the two or three classes involved in a one-to-many or many-to-many model association, and reconfigures these classes to make handling primary members of those associations simple.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(association_name, owning_class, options = {}) ⇒ Relationship 



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# File 'lib/prim/relationship.rb', line 11

def initialize association_name, owning_class, options = {}
  @options = options
  @association_name = association_name
  @owning_class = owning_class
  @reflection   = owning_class.reflect_on_association( association_name )

  # TODO: remove these exceptions and replace with logged errors? hmm.
  if reflection.nil?
    raise ArgumentError.new("Association '#{ association_name }' not found " +
      "on #{ owning_class.name }. Perhaps you misspelled it?")
  
  elsif !reflection.collection?
    raise SingularAssociationError.new("Association '#{ association_name }' " +
      "is not a one-to-many or many-to-many relationship, so it can't have a primary.")

  elsif !primary_column
    # TODO: add a generator to automatically create a migration, then change this
    # message to give users the exact instruction needed.
    raise InvalidPrimaryColumnError.new("#{ owning_class.name } needs table " +
      "`#{ mapping_reflection.table_name }` to have a boolean 'primary' column " +
      "in order to have a primary #{ source_class.name }.")
  end

  # TODO: ensure the association isn't nested?

  reflected_class.send :include, InstanceMethods::Reflected
  reflected_class.class_attribute :prim_relationship
  reflected_class.prim_relationship = self

  source_class.send :include, InstanceMethods::Source if mapping_table?
end

Instance Attribute Details

#association_name ⇒ Object (readonly)

Returns the value of attribute association_name.



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# File 'lib/prim/relationship.rb', line 8

def association_name
  @association_name
end

#options ⇒ Object (readonly)

Returns the value of attribute options.



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# File 'lib/prim/relationship.rb', line 8

def options
  @options
end

#owning_class ⇒ Object (readonly)

Returns the value of attribute owning_class.



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# File 'lib/prim/relationship.rb', line 8

def owning_class
  @owning_class
end

#reflection ⇒ Object (readonly)

Returns the value of attribute reflection.



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# File 'lib/prim/relationship.rb', line 8

def reflection
  @reflection
end

Instance Method Details

#collection_label ⇒ Object

The association method to call on the owning class to retrieve a record’s collection.



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# File 'lib/prim/relationship.rb', line 44

def collection_label
  (options[:through] || mapping_reflection.plural_name).to_sym
end

#mapping_reflection ⇒ Object

The association reflection representing the link between the owning class and the mapping class, whether or not the mapping class represents a join-table.



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# File 'lib/prim/relationship.rb', line 60

def mapping_reflection
  through_reflection || reflection
end

#mapping_table? ⇒ Boolean

True if this relationship relies on a mapping table for ‘primary` records.



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# File 'lib/prim/relationship.rb', line 65

def mapping_table?
  !!through_reflection
end

#reflected_class ⇒ Object

The class of the ‘mapping_reflection`.



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# File 'lib/prim/relationship.rb', line 54

def reflected_class
  mapping_reflection.klass
end

#source_class ⇒ Object

The class of the reflection source: i.e. Post if the owning class ‘has_many :posts`.



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# File 'lib/prim/relationship.rb', line 49

def source_class
  reflection.klass
end