Posts

Showing posts with the label activerecord

When Empty Isn’t Empty With Rails Active Record Collections

So I'm writing some Rails code, just playing around, and I run into a very strange situation. I've found a situation where Rails' Active Record code is calculating the results to empty? incorrectly, even if I add elements to the collection . So I had a has_many collection with elements inside of it, but calls to length or empty were returning 0 and true . Here's my simple models: class Query < ActiveRecord::Base has_many :measures validates_presence_of :cube_name def measure_attributes=(attrs) attrs.each {|a| measures.build(a)} end end and class Measure :query has_one :condition, :as => :conditionable end Notice that in Query, I've added a measure_attributes method which automatically handles the construction of new Measure instances from the form parameters. Here's the simple nested form. From the models, a Query has many Measures: <% form_for :query, :url => {:action => :new} do |f| %> Cube Name: <%= f.text_field :...
Read more

Encapsulate Relationships in Rails

It would be really nice if I could encapsulate all of the default accessors that are generated when I create a relationship between two ActiveRecord objects. For instance, when you declare that `has_and_belongs_to_many :people`, your model is peppered with public accessors for the people collection. These methods are generated for your class at runtime. I want to provide business logic around those people, and therefore I want to prohibit clients from directly accessing the people collection. I want to provide methods such as `register_person`. Of course, I can add that method, but there's nothing stopping someone from coming along and calling `model.people << person`. Is there? How to restrict direct access to the collection on an ActiveRecord model?
Read more

Add MetaData to your Models in Rails

Add metadata about your tables to your models in Rails . >Rails model files contain no information on the tables they represent. This is a good thing in general, because it reduces duplication—add a column to a table, and there’s no configuration to update in the model. >However, when you’re writing code, it’s sometimes nice to be able to see just what attributes a model has. >Enter annotate models, a really trivial Rails plugin I hacked up in the plane back from the first No Fluff of the year. The plugin adds a comment block to the top of each model file, documenting the schema. If you update the schema, run it again and it updates the comment.
Read more

Understanding Migrations in Ruby on Rails

UnderstandingMigrations in Ruby on Rails > ActiveRecordMigration allow you to use Ruby to define changes to your database schema, making it possible to use a version control system to keep things synchronised with the actual code.
Read more

Rails and Allowing ID Editing from Forms

Need to allow yours users to directly edit the ID of your model object? By default, Rails will strip out the ID field from the hash of request parameters. This is a security measure, prohibitings the web interface from altering an object's ID. Generally, this is a good practice. However, some legacy schemas have IDs that are not simply numbers. In those cases, the ID is created and managed by the user. To tell Rails to allow the ID to be edited, you can use attr_protected and attr_allowed . More information is available at http://wiki.rubyonrails.com/rails/pages/HowToEnsureValidAttributesInFormData
Read more

Rails, Legacy Schemas, ActiveRecord, and has_and_belongs_to_many

There turns out to be an issue with legacy schemas and ActiveRecord , the ORM layer of Rails when using has_and_belongs_to_many . Note: This issue might be Oracle specific. If the join table itself has an id column, and it has the same name as the id column from the association table, then it will override the id from the association table. This means that instances from the association table will have the wrong id. The solution looks to be the new :finder_sql parameter of the has_and_belongs_to_many relationship. With :finder_sql , you can override the generated SQL. How to use :finder_sql ? Try: has_and_belongs_to_many :ksaas, :join_table => "tbl_ksaa_objective", :foreign_key => "objective_cid", :association_foreign_key => "ksaa_cid", :finder_sql => "SELECT TBL_KSAA.cid, TBL_KSAA.ksaa_type, TBL_KSAA.ksaa_item, " + "TBL_KSAA.KSAA_TYPEID, TBL_KSAA.SAMPLE_BEHAVIOR " + "FROM TBL_KSAA LEFT JOIN TBL_KSAA_...
Read more

Using Columns with Reserved Names in Rails

From Rails Mailing List : How to access column with a reserved name? def new_column read_attribute 'old_column' end def new_column=(value) write_attribute 'old_column', value end
Read more