Rails: Postgres handling where clause – error in JSON format

Question

Hi I have a model books with below mentioned method:

def self.text_search(query)
    pry
    if query.present?
        where("title @@ :q or author @@ :q", q: query)
    else
        find(-1)
    end
end

In my controller, I send respond to client as JSON:

render json: @books

This code works fine if the query returns something. If not, I am not able to send a JSON response. I get a template missint error. How can I handle it in JSON?

I tried

class BooksController < ApplicationController
    def index
        @books = Book.text_search(params[:query])
        @author= Author.find(Shelf.find(@books.map(&:isbn).uniq).map(&:author_id))
        rescue ActiveRecord::RecordNotFound  #donothing

        render json: @books
    end
end

Hi Arup I have updated the question with controller. I realised that the issue is with my next database call. — Rigel
– Rigel, Commented Feb 29, 2016 at 7:58
no find(-1) give an empty book list. If Shelf has not books with the isbn we picked from books then , and for author I want to handle it — Rigel
– Rigel, Commented Feb 29, 2016 at 8:03

tobmatth · Accepted Answer · 2016-02-29 08:20:00Z

3

def self.text_search(query)
  if query.present?
    where("title @@ :q or author @@ :q", q: query)
  else
    Book.none
  end
end

should do the trick. Book.none returns an empty ActiveRecord::Relation.

In addition, i don't get why you assign authors while you only render @books.

@author= Author.find(Shelf.find(@books.map(&:isbn).uniq).map(&:author_id))

will raise ActiveRecord::RecordNotFound if no matching records present. Consider using find_by id: []

edited Feb 29, 2016 at 8:20

answered Feb 29, 2016 at 8:12

tobmatth

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2 Comments

Rigel Over a year ago

Hi tobmath thanks for Book.none trick will use it but it doesnt apply in this case I guess. I am passing a query so if query.present? is valid and where clause is executed. and in where clause finds nothing.Shelf.find is upset. and for that I am getting Missing template error. I can ignore and return only books but I dont know how to handle silently exception for Shelf.find

tobmatth Over a year ago

I don't know how your models are set up, but @author = Author.find_by(id: Shelf.find(@books.map(&:isbn).uniq).map(&:author_id)) should work.

jvillian · Accepted Answer · 2016-02-29 08:18:19Z

0

I like the thought from tobmatth. However, I also believe you should avoid throwing (and handling) exceptions in the normal (expected) flow of your code.

So, I'd also suggest something like:

class BooksController < ApplicationController
  def index
    @books = Book.text_search(params[:query])
    if @books.count > 0
      @author= Author.find(Shelf.find(@books.map(&:isbn).uniq).map(&:author_id))
    end

    render json: @books

  end
end

I think this would have worked with your original code (perhaps?).

answered Feb 29, 2016 at 8:18

jvillian

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