ActiveRecord find_or_build_by - ruby-on-rails

Question

I would like to perform:
XXX.find_or_build_by_language_id(attributes)
I found
XXX.find_or_initialize_by_language_id(attributes)
but that only set language_id and no other attributes. Even if I manually sets the attributes, the record is not saved when I perform XXX.save.
I just read Rails - find or create - is there a find or build?, which seems related to my problem but does not fit my needs.
Edit
Let's use this scenario
# db/migrations/create_models.rb
class CreateModels < ActiveRecord::Migration
def self.up
create_table :companies do |t|
t.string :name
end
create_table :employees do |t|
t.string :name
t.string :city
t.references :company
end
end
end
-
# app/models/employee.rb
class Employee < ActiveRecord::Base
belongs_to :company
end
-
# app/models/company.rb
class Company < ActiveRecord::Base
has_many :employees
end
-
# rails console
:001> c = Company.new
=> #<Company id: nil, name: nil>
:002> c.employees
=> []
:003> e = c.employees.find_or_initialize_by_name(:name => 'foo', :city => 'bar')
=> #<Employee id: nil, name: "foo", city: "bar", company_id: nil>
:004> c.employees
=> []
:005> c.save
=> true
:006> c.employees
=> []
:007> e.save
=> true
:008> c = Company.first
=> #<Company id: 1, name: nil>
:009> c.employees
=> [#<Employee id: 1, name: "foo", city: "bar", company_id: 1>]
:010> e = c.employees.find_or_initialize_by_name(:name => 'foo', :city => 'baz')
=> #<Employee id: 1, name: "foo", city: "bar", company_id: 1>
:011> e.city = 'baz'
=> "baz"
:012> c.employees
=> [#<Employee id: 1, name: "foo", city: "bar", company_id: 1>]
:013 > c.save
=> true
:014> c.employees
=> [#<Employee id: 1, name: "foo", city: "bar", company_id: 1>]
Problems
:004 => The Employee from :003 is not added to c.employees
:006 => The Employee from :003 is saved with c
:010 => The city attribute of employee is not set
:014 => THe city attribute of employee is not updated when saving company

Answer 1

How about this?
employee_attrs = {:name => 'foo', :city => 'bar'}
e = c.employees.where(employee_attrs).first || c.employees.build(employee_attrs)

Answer 2

For the record, here is the implementation I came with. It can probably be simpler, but it suits my needs:
module ActiveRecord
module Associations
class AssociationCollection < AssociationProxy
alias_method :old_method_missing, :method_missing
def method_missing(method_id, *arguments, &block)
if /^find_or_build_by_([_a-zA-Z]\w*)$/ =~ method_id.to_s
names = $1.split('_and_')
find_or_build_by(names, *arguments)
else
old_method_missing(method_id, *arguments, &block)
end
end
def find_or_build_by(names, *arguments)
values = arguments[0]
throw InvalidArgument unless values.keys.first.kind_of?(String)
record = Array.new(self).find do |r|
names.inject(true) do |memo, name|
memo && (values[name].to_s == r.send(name).to_s)
end
end
if record
sanitized_values = record.send(:sanitize_for_mass_assignment, values)
sanitized_values.each {|k, v| record.send("#{k}=", v)}
else
record = build(values)
end
return record
end
end
end
end

Answer 3

I tried the following code for my Rails 4.2.x app.
#config/initializers/collection_proxy.rb
ActiveRecord::Associations::CollectionProxy.class_eval do
alias_method :old_method_missing, :method_missing
def method_missing(method_id, *arguments, &block)
if /^find_or_build_by([_a-zA-Z]\w*)$/ =~ method_id.to_s
names = $1.split('_and_')
find_or_build_by(names, *arguments)
else
old_method_missing(method_id, *arguments, &block)
end
end
def find_or_build_by(names, *arguments)
where(names).first || build(names)
end
end
You can use it like this.
XXX.find_or_build_by(attributes)