Class: DBDiagram::Domain::Relationship

Inherits:
Object
  • Object
show all
Extended by:
Inspectable
Defined in:
lib/db_diagram/domain/relationship.rb,
lib/db_diagram/domain/relationship/cardinality.rb

Overview

Describes a relationship between two entities. A relationship is detected based on Active Record associations. One relationship may represent more than one association, however. Related associations are grouped together. Associations are related if they share the same foreign key, or the same join table in the case of many-to-many associations.

Defined Under Namespace

Classes: Cardinality

Constant Summary collapse

N = 
Cardinality::N

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Inspectable

inspection_attributes

Constructor Details

#initialize(domain, associations) ⇒ Relationship

Returns a new instance of Relationship.



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# File 'lib/db_diagram/domain/relationship.rb', line 63

def initialize(domain, associations) # @private :nodoc:
  @domain = domain
  @reverse_associations, @forward_associations = partition_associations(associations)

  assoc = @forward_associations.first || @reverse_associations.first
  @source      = @domain.entity_by_name(self.class.send(:association_owner, assoc))
  @destination = @domain.entity_by_name(self.class.send(:association_target, assoc))
  @source, @destination = @destination, @source if assoc.belongs_to?
end

Instance Attribute Details

#destination ⇒ Object (readonly)

The destination entity. It corresponds to the model that has defined a belongs_to association with the other model.



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# File 'lib/db_diagram/domain/relationship.rb', line 58

def destination
  @destination
end

#domain ⇒ Object (readonly)

The domain in which this relationship is defined.



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# File 'lib/db_diagram/domain/relationship.rb', line 50

def domain
  @domain
end

#source ⇒ Object (readonly)

The source entity. It corresponds to the model that has defined a has_one or has_many association with the other model.



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# File 'lib/db_diagram/domain/relationship.rb', line 54

def source
  @source
end

Class Method Details

.from_associations(domain, associations) ⇒ Object 



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# File 'lib/db_diagram/domain/relationship.rb', line 16

def from_associations(domain, associations) # @private :nodoc:
  assoc_groups = associations.group_by { |assoc| association_identity(assoc) }
  assoc_groups.collect { |_, assoc_group| new(domain, assoc_group.to_a) }
end

Instance Method Details

#<=>(other) ⇒ Object 



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# File 'lib/db_diagram/domain/relationship.rb', line 133

def <=>(other) # @private :nodoc:
  (source.name <=> other.source.name).nonzero? or (destination.name <=> other.destination.name)
end

#associations ⇒ Object

Returns all Active Record association objects that describe this relationship.



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# File 'lib/db_diagram/domain/relationship.rb', line 75

def associations
  @forward_associations + @reverse_associations
end

#cardinality ⇒ Object

Returns the cardinality of this relationship.



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# File 'lib/db_diagram/domain/relationship.rb', line 80

def cardinality
  @cardinality ||= begin
    reverse_max = any_habtm?(associations) ? N : 1
    forward_range = associations_range(@forward_associations, N)
    reverse_range = associations_range(@reverse_associations, reverse_max)
    Cardinality.new(reverse_range, forward_range)
  end
end

#many_to? ⇒ Boolean

Indicates whether the source cardinality class of this relationship is equal to infinity. This is true for many-to-many relationships only.

Returns:

  • (Boolean) 


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# File 'lib/db_diagram/domain/relationship.rb', line 123

def many_to?
  cardinality.cardinality_class[0] != 1
end

#mutual? ⇒ Boolean

Indicates whether or not the relationship is defined by two inverse associations (e.g. a has_many and a corresponding belongs_to association).

Returns:

  • (Boolean) 


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# File 'lib/db_diagram/domain/relationship.rb', line 92

def mutual?
  @forward_associations.any? and @reverse_associations.any?
end

#one_to? ⇒ Boolean

Indicates whether the source cardinality class of this relationship is equal to one. This is true for one-to-one or one-to-many relationships only.

Returns:

  • (Boolean) 


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# File 'lib/db_diagram/domain/relationship.rb', line 117

def one_to?
  cardinality.cardinality_class[0] == 1
end

#recursive? ⇒ Boolean

Indicates whether or not this relationship connects an entity with itself.

Returns:

  • (Boolean) 


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# File 'lib/db_diagram/domain/relationship.rb', line 97

def recursive?
  @source == @destination
end

#strength ⇒ Object

The strength of a relationship is equal to the number of associations that describe it.



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# File 'lib/db_diagram/domain/relationship.rb', line 129

def strength
  if source.generalized? then 1 else associations.size end
end

#to_many? ⇒ Boolean

Indicates whether the destination cardinality class of this relationship is equal to infinity. This is true for one-to-many or many-to-many relationships only.

Returns:

  • (Boolean) 


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# File 'lib/db_diagram/domain/relationship.rb', line 110

def to_many?
  cardinality.cardinality_class[1] != 1
end

#to_one? ⇒ Boolean

Indicates whether the destination cardinality class of this relationship is equal to one. This is true for one-to-one relationships only.

Returns:

  • (Boolean) 


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# File 'lib/db_diagram/domain/relationship.rb', line 103

def to_one?
  cardinality.cardinality_class[1] == 1
end