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  • Saving a Record with Rails Association

    - by tshauck
    Hi, I've been going through the Rails Guides, but have gotten stuck on associations after going through validations and migrations. So, I have the following models Job and Person, where a Person can have many jobs. I know that in reality there'd be a many-to-many, but I'm trying to get my handle on this first. class Job < ActiveRecord::Base belongs_to :people end and class Person < ActiveRecord::Base has_many :jobs end Here's the schema ActiveRecord::Schema.define(:version => 20110108185924) do create_table "jobs", :force => true do |t| t.string "occupation" t.boolean "like" t.datetime "created_at" t.datetime "updated_at" t.integer "person_id" end create_table "people", :force => true do |t| t.string "first_name" t.string "last_name" t.datetime "created_at" t.datetime "updated_at" end end Is there some I can do the following j = Job.first; j.Person? Then that'd give me access to the Person object associated with the j. I couldn't find it on guides.rubyonrails.org, although it has been very helpful getting a grip on migrations and validations thus far. Thanks PS, If there are any tutorials that covers more of this kind of things links would be great.

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  • ordering a collection by an association's property

    - by neiled
    class Person belongs_to :team class Status #has last_updated property class Team has_many :members, :class => "Person" Ok, so I have a Team class which has many People in it and each of those people has a status and each status has a last_updated property. I'm currently rendering a partial with a collection similar to: =render :partial => "user", :collection => current_user.team.members Now how do I go about sorting the collection by the last_updated property of the Status class? Thanks in advance! p.s. I've just written the ruby code from memory, it's just an example, it's not meant to compile but I hope you get the idea!

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  • Rails: validate presence of parent_id in has_many association

    - by deb
    I have a projects resource that has many tasks. I want to ensure that every task has a project_id by adding validates_presence_of :project_id to the tasks model. However, when creating a new project with tasks, the project_id won't be available until the record saves, therefore I can't use validates_presence_of :project_id. So my question is, how do I validate presence of project_id in the task model? I want to ensure every task has a parent. ... class Project < ActiveRecord::Base has_many :tasks, :dependent => :destroy accepts_nested_attributes_for :tasks, :allow_destroy => true ... class Task < ActiveRecord::Base belongs_to :project validates_presence_of :project_id

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  • How to set up two models having a has_many association with each other

    - by daz13
    I'm looking for a suggestion on how to set up two models, Teacher and Subject. A Teacher can have many Subjects, and a Subject can have many Teachers. Another thing to consider in the relationship between the two models is that a Teacher can create a Subject and add other Teachers to the Subject. I think I'm solid on the basics of the set up for each model: for teacher.rb: has_many :subjects for subject.rb: has_many :teachers and the teachers table should have a subject_id column and the subject table should have a teacher_id column. What I'm not sure about is how to set up the views (and corresponding controller methods) to allow the addition of a Teacher to a Subject. Any suggestions (or links to examples) are greatly appreciated. I haven't been able to find anything on this exact case.

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  • Creating an instance in rails association

    - by Sandeep Rao
    I have three models where a basiccase has a form. Basic case can create a new form. class User < ActiveRecord::Base has_many :basiccases end class Basiccase < ActiveRecord::Base belongs_to :user has_one :basiccases end class Form3C < ActiveRecord::Base belongs_to :basiccases end I want to create an instance of form 3c in the form3c controller. Can any one explain me how I can carry the basiccase_id to the form3c controller to set the foreign key attribute. I can set the value using @basiccase.build_form3_c but I'm not sure how I can get the basiccase_id from the basiccase.

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  • Rails - How to secure foreign keys and still allow association selection

    - by Bryce
    For simplicity, assume that I have a simple has-many-through relationship class User < ActiveRecord::Base has_many :courses, :through => :registrations end class Registration < ActiveRecord::Base belongs_to :user belongs_to :course end class Course < ActiveRecord::Base has_many :users, :through => :registrations end I want to keep my app secure, so I use attr_accessible to whitelist my attributes. My question is twofold: How would I set up my whitelist attributes such that I could create a new Registration object through a form (passing in :user and :course, but not risk allowing those foreign keys to be maliciously updated later? How would I set up my validations such that both belongs_to associations are required BUT also allow for Registration objects to be created in nested forms?

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  • Rails find all with association

    - by aaronrussell
    I have what I think is a very simple problem (famous last words)... I have a Category model that has_and_belongs_to_many Events. I want to construct a simple and efficient query that finds all categories that have 1 or more events. (using Rails 3) I'm sure I'm having a dumb moment here - any help appreciated :)

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  • Rails find through association

    - by yogi
    class Customer < ActiveRecord::Base has_one :address, :foreign_key => "customerid" end class Address < ActiveRecord::Base belongs_to :customer, :foreign_key => "customerid" end How do I find records in customer that do not have customerid in address table? in SQL i'd do select * from customer a, address b where a.customerid <> b.customerid

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  • finding elements in python association lists efficiently

    - by user248237
    I have a set of lists that look like this: conditions = [ ["condition1", ["sample1", "sample2", "sample3"]], ["condition2", ["sample4", "sample5", "sample6"], ...] how can I do the following things efficiently and elegantly in Python? Find all the elements in a certain condition? e.g. get all the samples in condition2. Right now I can do: for cond in conditions: cond_name, samples = cond if cond_name == requested_cond: return samples but that's clunky. Find the ordered union of a list of conditions? E.g. ordered_union(["condition1", "condition2"], conditions) should return: ["sample1", "sample2", "sample3", "sample4", "sample5", "sample6"] How can I do this efficiently in Python? There are probably clever one liners?

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  • Rails Scope for association of 0 size.

    - by MissingHandle
    I'm having trouble figuring out the scope method for all the Foos that have no Bars. That is: class Foo < ActiveRecord::Base has_may :bars end class Bar < ActiveRecord::Base belongs_to :foo end I'd like to write a scope method that returns me all the foos that have no bars. Something like: class Foo < ActiveRecord::Base has_may :bars scope :has_no_bars, includes(:bars).where("COUNT(foo.bars) = 0") end But I don't understand the appropriate syntax. Any help? Happy to use a MetaWhere solution if easier.

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  • Rails Association Question...

    - by keruilin
    I have three models: User, RaceWeek, Race # Current associations: User has_many race_weeks; RaceWeek belongs to user; RaceWeek has many races; Race belongs to RaceWeek # So the user_id is a foreign key in RaceWeek and race_week_id is a foreign key in Race. # fastest_time is an attribute of the Race model. # QUESTION: What's the optimal way to retrieve a list of users who have the top X fastest race times?

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  • In a bidirectional JPA OneToMany/ManyToOne association, what is meant by "the inverse side of the as

    - by Bytecode Ninja
    In these examples on TopLink JPA Annotation Reference: Example 1-59 @OneToMany - Customer Class With Generics @Entity public class Customer implements Serializable { ... @OneToMany(cascade=ALL, mappedBy="customer") public Set<Order> getOrders() { return orders; } ... } Example 1-60 @ManyToOne - Order Class With Generics @Entity public class Order implements Serializable { ... @ManyToOne @JoinColumn(name="CUST_ID", nullable=false) public Customer getCustomer() { return customer; } ... } It seams to me that the Customer entity is the owner of the association. However, in the explanation for the mappedBy attribute in the same document, it is written that: if the relationship is bidirectional, then set the mappedBy element on the inverse (non-owning) side of the association to the name of the field or property that owns the relationship as Example 1-60 shows. However, if I am not wrong, looks like in the example the mappedBy is actually specified on the owning side of the association, rather than the non-owning side. So my question is basically: In a bidirectional (one-to-many/many-to-one) association, which of the entities is the owner? How can we designate the One side as the owner? How can we designate the Many side as the owner? What is meant by "the inverse side of the association"? How can we designate the One side as the inverse? How can we designate the Many side as the inverse? Thanks in advance.

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  • I removed my WinXP machine's association to U1 from within the Windows client, and now can't get it back to work anymore

    - by Andrea
    After testing the windows client for U1 sync, I decided to test the preferences' settings, and tried to remove the association for the WinXP station from which I was working. Now I can start the client, but if I try to open the preferences' settings the application stops. I tried to uninstalle and reinstall, but that won't change the situation: appearently the old settings are kept the same even after a total reinstall.

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  • Working with EO composition associations via ADF BC SDO web services

    - by Chris Muir
    ADF Business Components support the ability to publish the underlying Application Modules (AMs) and View Objects (VOs) as web services through Service Data Objects (SDOs).  This blog post looks at a minor challenge to overcome when using SDOs and Entity Objects (EOs) that use a composition association. Using the default ADF BC EO association behaviour ADF BC components allow you to work with VOs that are based on EOs that are a part of a parent-child composition association.  A composition association enforces that you cannot create records for the child outside the context of the parent.  As example when creating invoice-lines you want to enforce the individual lines have a relating parent invoice record, it just simply doesn't make sense to save invoice-lines without their parent invoice record. In the following screenshot using the ADF BC Tester it demonstrates the correct way to create a child Employees record as part of a composition association with Departments: And the following screenshot shows you the wrong way to create an Employee record: Note the error which is enforced by the composition association: (oracle.jbo.InvalidOwnerException) JBO-25030: Detail entity Employees with row key null cannot find or invalidate its owning entity.  Working with composition associations via the SDO web services  Shay Shmeltzer recently recorded a good video which demonstrates how to expose your ADF Business Components through the SDO interface. On exposing the VOs you get a choice of operation to publish including create, update, delete and more: For example through the SDO test interface we can see that the create operation will request the attributes for the VO exposed, in this case EmployeesView1: In this specific case though, just like the ADF BC Tester, an attempt to create this record will fail with JBO-25030, the composition association is still enforced: The correct way to to do this is through the create operation on the DepartmentsView1 which also lets you create employees record in context of the parent, thus satisfying the composition association rule: Yet at issue here is the create operation will always create both the parent Departments and Employees records.  What do we do if we've already previously created the parent Departments records, and we just want to create additional Employees records for that Department?  The create method of the EmployeeView1 as we saw previously doesn't allow us to do that, the JBO-3050 error will be raised. The solution is the "merge" operation on the parent Departments record: In this case for the Departments record you just need to supply the DepartmentId of the Department you want the Employees record to be associated with, as well as the new Employees record.  When invoked only the Employees record is created, and the supply of the DepartmentId of the Departments record satisfies the composition association without actually creating or updating the associated Department record that already exists in the database. Be warned however if you supply any more attributes for the Department record, it will result in a merge (update) of the associated Departments record too. 

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  • Rails Associations - Callback Sequence/Magic

    - by satynos
    Taking following association declaration as an example: class Post has_many :comments end Just by declaring the has_many :comments, ActiveRecord adds several methods of which I am particularly interested in comments which returns array of comments. I browsed through the code and following seems to be the callback sequence: def has_many(association_id, options = {}, &extension) reflection = create_has_many_reflection(association_id, options, &extension) configure_dependency_for_has_many(reflection) add_association_callbacks(reflection.name, reflection.options) if options[:through] collection_accessor_methods(reflection, HasManyThroughAssociation) else collection_accessor_methods(reflection, HasManyAssociation) end end def collection_accessor_methods(reflection, association_proxy_class, writer = true) collection_reader_method(reflection, association_proxy_class) if writer define_method("#{reflection.name}=") do |new_value| # Loads proxy class instance (defined in collection_reader_method) if not already loaded association = send(reflection.name) association.replace(new_value) association end define_method("#{reflection.name.to_s.singularize}_ids=") do |new_value| ids = (new_value || []).reject { |nid| nid.blank? } send("#{reflection.name}=", reflection.class_name.constantize.find(ids)) end end end def collection_reader_method(reflection, association_proxy_class) define_method(reflection.name) do |*params| force_reload = params.first unless params.empty? association = association_instance_get(reflection.name) unless association association = association_proxy_class.new(self, reflection) association_instance_set(reflection.name, association) end association.reload if force_reload association end define_method("#{reflection.name.to_s.singularize}_ids") do if send(reflection.name).loaded? || reflection.options[:finder_sql] send(reflection.name).map(&:id) else send(reflection.name).all(:select => "#{reflection.quoted_table_name}.#{reflection.klass.primary_key}").map(&:id) end end end In this sequence of callbacks, where exactly is the actual SQL being executed for retrieving the comments when I do @post.comments ?

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  • ruby, rails, railscasts example gone bad

    - by Sam
    If you saw the railscasts on nested forms this is the helper method to create links dynamically. However, after I upgraded to ruby 1.9.2 and rails 3 this doesn't work and I have now idea why. def link_to_add_fields(name, f, association) new_object = f.object.class.reflect_on_association(association).klass.new fields = f.fields_for(association, new_object, :child_index => "new_#{association}") do |builder| render(association.to_s.singularize + "_fields", :f => builder) end link_to_function(name, h("add_fields(this, \"#{association}\", \"#{escape_javascript(fields)}\")")) end here is the javascript function add_fields(link, association, content) { var new_id = new Date().getTime(); var regexp = new RegExp("new_" + association, "g") $(link).up().insert({ before: content.replace(regexp, new_id) }); }

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  • Is there a way to add extra fields to an association in the ADO.NET Entity Framework?

    - by bigbird1040
    I would like to be able to model a many-to-many relationship that has extra details about the relationship. For example: Person: int id, String name Project: int id, String name ProjectPerson: Person.id, Project.id, String role Whenever I create the ProjectPerson association in the EF, I am unable to add the role attribute to the association. If I create the tables in my DB and then import it into the model, I lose the extra properties.

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  • Preloading data without messing up association when data is loaded the 2nd time.

    - by denniss
    This is how my model looks like User belongs_to :computer Computer has_many :user Users are created when people register for an account on the web site but computers are pre-loaded data that I create in seeds.rb/some .rake file. All is fine and good when the app is first launched and people start registering and get associated with the right computer_id. However, suppose I want to add another computer to the list Computer.destroy_all Computer.create({:name => "Akane"}) Computer.create({:name => "Yoda"}) Computer.create({:name => "Mojito"}) #newly added running the rakefile the second time around will mess up the associations because computer_id in the User table refer to the old id in Computer table. Since I have run the script above, the id keeps incrementing without any regard to the association that user has to it. Question: Is there a better way for me to pre-load data without screwing up my association? I want to be able to add new Computer without having to destroy the user's table. Destroying the computer table is fine with me and rebuilding it again but the old association that the existing users have must stay intact.

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  • New SSIS features and enhancements in Denali – a webinar on 28th June in association with Pragmatic Works

    - by jamiet
    Tomorrow I shall be presenting a webinar entitled “New SSIS features and enhancements in Denali”. The webinar is being hosted by Pragmatic Works and you can sign up for it at Pragmatic Works webinars. The webinar will start at 1930BST and you can view the time for your timezone at this link: http://www.timeanddate.com/worldclock/fixedtime.html?msg=New+SSIS+features+and+enhancements+in+Denali&iso=20110628T1830 The webinar was arranged a few months ago and at that time we were hoping that the next Community Technology Preview (CTP) of SQL Server Denali would be available for public consumption; unfortunately it transpires that that is not yet the case and hence I will be presenting new features of CTP1 that was released at the start of this year. If you’re not yet familiar with the new features of SSIS that are coming in the next release of SQL Server then please do come and join the webinar. @Jamiet

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  • File / Application association using a custom command is gone?

    - by Christian Vielma
    In previous Ubuntus when you want to select/change an application to open a specific file (right-click/open with other application or properties) you were able to write a custom command to open the file. This was very useful, but now in 11.10 I can't find this option, it only shows me a list of applications and a button to look for applications in Internet. Is there a way to restore the command line to write custom commands to open files?

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  • PHP MVC: How to implement an effective Controller/View Association like ZendFramework guys do!

    - by Navi
    Hi, I am making my own PHP-MVC framework. i have a question regarding Controller and View Association. I love the way Zend framework uses view within Controller as follow: $this->view->data = 'Data here'; so it can be used in view as follow: echo $this->data; I am wondering how can i implement this association. I want to remove codes between /** **/ and want to replace with some magic functions. My codes for controller as as follow: class UserController extends Controller{ /************************************/ public function __construct(){ $this->view = new View(); $this->view->setLayout( 'home' ); } function __destruct(){ $this->view->render(); } /************************************/ public function index(){ $this->redirect('user/login'); } public function login(){ } public function register(){ } public function forgotPassword(){ } } Thanks and best regards, -Navi

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  • Model association changes in production environment, specifically converting a model to polymorphic?

    - by dustmoo
    Hi everyone, I was hoping I could get feedback on major changes to how a model works in an app that is in production already. In my case I have a model Record, that has_many PhoneNumbers. Currently it is a typical has_many belongs_to association with a record having many PhoneNumbers. Of course, I now have a feature of adding temporary, user generated records and these records will have PhoneNumbers too. I 'could' just add the user_record_id to the PhoneNumber model, but wouldn't it be better for this to be a polymorphic association? And if so, if you change how a model associates, how in the heck would I update the production database without breaking everything? .< Anyway, just looking for best practices in a situation like this. Thanks!

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