ActiveRecord find_or_build_by

Question

我想表演:

    XXX.find_or_build_by_language_id(attributes)

我发现

    XXX.find_or_initialize_by_language_id(attributes)

但这只设置了language_id而没有其他属性.即使我手动设置属性,当我执行XXX.save时也不会保存记录.

我只是阅读Rails - 查找或创建 - 是否有查找或构建？,这似乎与我的问题有关,但不符合我的需要.

编辑

让我们使用这个场景

# 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>]

问题

1. :004 =>来自:003的员工未添加到c.employees
2. :006 =>来自:003的员工用c保存
3. :010 =>未设置员工的城市属性
4. :014 =>保存公司时员工的城市属性未更新

Answer 1

这个怎么样？

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