Api :: SessionsController＃create中的NoMethodError

Question

I keep getting this error in my sessions controller in my rails 5 api:

undefined method `[]' for nil:NilClass

I'm honestly not sure what i'm doing wrong. Here is my code for my sessions controller (error occurs on line 8):

module Api
class SessionsController < ApplicationController

def new
end

def create
  # The error occurs on this line
  @user = @User.find_by(email: params[:session][:email].downcase)
    if user && user.authenticate(params[:session][:password])
      render :text => user.access_token, status: 200
    else
      render text: "Email and password combination are invalid", status: 422
    end
end


def verify_access_token
  user = User.find_by(access_token: params[:session][:access_token])
    if user
      render text: "verified", status: 200
    else
      render text: "Token failed verification", status: 422
    end
  end

 end
end

here is my sesssions helper:

module SessionsHelper
# Logs in the given user.
def log_in(user)
session[:user_id] = user.id
end

# Remembers a user in a persistent session.
# signed creates an encrypted cookie so that's why we use it.
def remember(user)
  user.remember
  cookies.permanent.signed[:user_id] = user.id
  cookies.permanent[:remember_token] = user.remember_token
end

# Returns true if the given user is the current user.
def current_user?(user)
  user == current_user
end

# Returns the current logged-in user (if any).
def current_user
  if (user_id = session[:user_id])
   @current_user ||= User.find_by(id: user_id)
  elsif (user_id = cookies.signed[:user_id])
    user = User.find_by(id: user_id)
    if user && user.authenticated?(cookies[:remember_token])
    log_in user
    @current_user = user
   end
 end
end

# Returns true if the user is logged in, false otherwise.
def logged_in?
 !current_user.nil?
end

# Forgets a persistent session.
def forget(user)
  user.forget
  cookies.delete(:user_id)
  cookies.delete(:remember_token)
end

def log_out
  forget(current_user)
  session.delete(:user_id)
  @current_user = nil
end

# Redirects to stored location (or to the default).
def redirect_back_or(default)
  redirect_to(session[:forwarding_url] || default)
  session.delete(:forwarding_url)
end

# Stores the URL trying to be accessed.
def store_location
  session[:forwarding_url] = request.url if request.get?
end

If anyone can help help me find a solution to this error, it would be deeply appreciated. I'm pretty new when it comes to JSON api's.

Answer 1

I'm betting params[:session] is nil. This is why chaining hash keys is a bad idea.

See also Hash#dig https://ruby-doc.org/core-2.3.0/Hash.html#method-i-dig

(which is news to me!)

Answer 2

@User is not a valid way to look up ActiveRecord objects. It should be the name of the model, capitalized, then the find method.

Change @user = @user... to to @user = User.find_by... and you should be able to complete the lookup properly.

One thing I like to do is drop a byebug above the line in question and then build up the query 'dot-by-dot' in the terminal to see if I can find where I've gone wrong. It will also let you look inside the params to make sure there is something there.