Select without the id field (RoR)

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I'm having a very silly question, I'm doing a system with Ruby on Rails and I need to do a select where the id field does not come, the problem is that this field is always present, for example: Employee.select('nome, email').all

The above code should return several records and bring only the name and email fields as I am configuring, as with other fields, however the id gets nil but does not disappear, the record looks like this: 

{
  id: null,
  name: "CRISTINA EXEMPLO",
  email: "Executiva de Atendimento"
}

How do I remove this field objectively, because I know I could iterate over the result and create a simple list, but I believe that rails support resolving this without major maneuvers.

I hope to have been clear and I'm waiting for a little help, vlw.

    
asked by anonymous 19.11.2015 / 15:47

4 answers

1

Alessandro, this is a complicated question and requires us to understand some things:

1) If you want to return an object without the id attribute, Rails will not do this, and I'll explain why:

You have created a class, the ActiveRecord model that is implicitly bound to the bank records. As in Rails everything is by convention, it admits that its class declares the attributes referring to the fields of the table to which it is bound. And we know that every object generated by a class must respect its methods and attributes in which the class has defined. So, if you create (implicitly) a class that has the id attribute, how could you have an object generated by this class without this attribute?

If you really want an object that contains only the attributes that suit you, you should encapsulate this result into another object defined by a new class (it could be a Struct or OpenStruct itself). It would act as a DTO (Data Transfer Object) .

2) If you want to return a default hash, only with these fields:

Well, there you should loop and mount your Hash , there is no way, because Rails as quoted above, will always respect the contract defined by the class (implicitly). So even if you ask for it to return as a Hash object, it will be based on the attributes of your model.

My suggestion

If you want to return an object of type Hash or another object that you want to set (option 1), why do not you create a method in your model that does this for you. The iteration to create a hash or mount a new object (could be Struct ) is very simple, and you would not expose it to the rest of the application. Something like: 

class Employee < ActiveRecord::Base
  def self.all_with_fields_that_i_want
    all.map do |e|
      OpenStruct.new({name: e.name, email: e.email})
    end
  end
end

results = Employee.all_with_fields_that_i_want
    
05.05.2016 / 21:00
0
Model.select('field AS field_one').first.field_one   
# => "value"

I checked the method documentation select see if that works.

    
22.11.2015 / 02:43
0

You can also use the active record and make a map 

Model.where(name: 'Cristina', email: '[email protected]').map{|m| {name: m.name, email: m.email}}
    
23.11.2015 / 20:59
0

You can use method except

  

link

Example 

Model.find(10).order('id asc').except(:id)

Or at the time of mounting a .each you can reject a: field

Example 

<% @model.reject(&:password_digest?).each do |attribute| %>
    
17.12.2015 / 14:58
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