从Rails中的活动记录中获取特定的列值

Question

I want to fetch a specific column value from active records, i wrote the sql query in view but I did not get the data... new.html.erb

 <%= f.text_field :pan_number, { value: OfferLetter.where(["candidate_id = (?)",params[:userID]]).select("pan_number").first, placeholder: 'COYP1234IN', class: 'form-control' } %>

then I got following result in my view

OfferLetter.where(["candidate_id = ?",17]).select("pan_number")


OfferLetter Load (0.3ms)  SELECT `offer_letters`.`pan_number` FROM `offer_letters` WHERE (candidate_id = 17)
=> #<ActiveRecord::Relation [#<OfferLetter id: nil, pan_number: "COPYD123IN">]>

and new.html.page here Pan Card number is not display

please help me i am new in ruby on rails and tell me where am i wrong and what is issue

Answer 1

You can use pluck for this, see http://apidock.com/rails/ActiveRecord/Calculations/pluck

In your case try Following:

OfferLetter.where("candidate_id = ?", params[:userID]).pluck("pan_number").first

And

As you are new to ror, following is to help you with way ahead:

Do write the ActiveRecord queries in Models only for faster query execution, not in view, controller etc.

So in this cases try to have a class method like 'get_pan_number' at Model and use it in view.

OfferLetter.rb

def self.get_pan_number(cand_id)
 OfferLetter.where("candidate_id = ?", cand_id).pluck("pan_number").first
end

And in the view use it as follows:

new.html.erb

<% pan_no = OfferLetter.get_pan_number(params[:userID]) %>
<%= f.text_field :pan_number, { value: pan_no, placeholder: 'COYP1234IN', class: 'form-control' } %>