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How to navigate through association class to create constraints with OCL?


By : Pam Goodvin
Date : October 14 2020, 08:10 PM
will help you You looking at a very dark corner. My first attempts at actually testing this functionality foundered on a failure to find a UML tool that could actually draw Fig 7.1. Once I got to grips with the text I realized there are many problems; a potential conflict between two different x[y] syntaxes, further aggravated by a QVTo shortform. There is a problem with extension to more than binary associations. The OCL Abstract Syntax continues to use the UML 1.x concepts of AssociationEnd rather than the UML 2.x Property.
Consequently the functionality you observe is the result of the best endeavours of some tool vendor to make sense of a very inadequate specification.
code :


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Create a many-to-many association for more of 2 classes through a relationship class


By : douwe
Date : March 29 2020, 07:55 AM
I wish this help you I am using Ruby on Rails 3 and I would like to set a many-to-many association for more of 2 classes through a relationship class. , You could use a polymorphic assocation through a join table.
code :
class RelationshipGroup < ActiveRecord::Base # This is the relationship class
  has_many :memberships
  has_many :members, :through => :memberships
end 

class Membership
  #fields - relationship_group_id, member_id, member_type
  belongs_to :relationship_group
  belongs_to :member, :polymorphic => true
end

class Dog < ActiveRecord::Base
  has_many :memberships, :as => :member
  has_many :relationship_groups, :through => :memberships
end 

class Cat < ActiveRecord::Base
  has_many :memberships, :as => :member
  has_many :relationship_groups, :through => :memberships    
end 

class Cow < ActiveRecord::Base
  has_many :memberships, :as => :member
  has_many :relationship_groups, :through => :memberships    
end 
#in lib/member.rb
module Member
  def self.included(base)
    base.class_eval do 
      has_many :memberships, :as => :member
      has_many :relationship_groups, :through => :memberships   
    end    
  end     
end 

class RelationshipGroup < ActiveRecord::Base # This is the relationship class
  has_many :memberships
  has_many :members, :through => :memberships
end 

class Membership
  #fields - relationship_group_id, member_id, member_type
  belongs_to :relationship_group
  belongs_to :member, :polymorphic => true
end

class Dog < ActiveRecord::Base
  include Member
end 

class Cat < ActiveRecord::Base
  include Member 
end 

class Cow < ActiveRecord::Base
  include Member
end 

DBIx::Class::ResultSet Update or Create on multiple unique constraints


By : Atomic Llama
Date : March 29 2020, 07:55 AM
Hope this helps I figured it out: you have to define the unique constraint in the Controller with add_unique_constraint.

Activerecord-association: create new object (find class)


By : Keah Peters
Date : March 29 2020, 07:55 AM
Any of those help You can also use build_association() in the relationship classes.
Simplest way to use it is through the Model's __call, i.e. if your relation is something like $person->company, then you could instantiate the company with

How to create an association class in draw.io?


By : Pye Wallace
Date : March 29 2020, 07:55 AM
should help you out draw.io is a drawing tool, not a UML tool.
As such you can simply draw two class shapes, connect them with an association shape, then draw a third class as you association class and then use an association shape to connect you association class to the association.

Doctrine 2 association without foreign key constraints


By : Carlos Medina
Date : March 29 2020, 07:55 AM
Does that help I had to go through the same process recently and fortunately there is an easy solution, just add nullable=true to the column's annotation.
This will work as long as the existing data is valid, in my case I had to change 0's to NULL's and change keys that didn't exist anymore to NULL.
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