no implicit conversion of nil into String Ruby on Rails - ruby-on-rails

Question

can somebody help with this, please?
My blog post share isn't showing an image on Twitter. I benchmarked other websites and noticed all the blog post working websites had a domain URL in the prior to the image URL. So, I added on it and blog post started working!!!. Yayy
Then, I've encountered another problem. When I click to see a blog page, it shows an error message(per below)
ActionView::Template::Error (no implicit conversion of nil into String):
21: %meta{:content => "https://www.joynus.com"+#post.preview_image.try(:data).try(:url), :name => "twitter:image"}
My post controller
class PostsController < ApplicationController
before_filter :authorize, only: [:edit, :update, :new, :create, :destroy]
before_filter :find_post, only: [:show, :edit, :update, :destroy]
def index
#posts = Post.order("created_at DESC").page(params[:page]).per(9)
respond_to do |format|
format.html
format.rss { render :layout =>false }
end
end
def show
end
def new
#post = Post.new
end
def create
#post = Post.new(post_params)
if #post.save
redirect_to posts_url
else
render 'new'
end
end
def edit
end
def update
if #post.update_attributes(post_params)
redirect_to post_url(#post), notice: "#{#post.title} Updated"
else
render 'edit'
end
end
def destroy
#post.destroy
redirect_to posts_url, notice: "#{#post.title} Deleted"
end
private
def post_params
params.require(:post).permit(:title, :social_title, :contents, :author_id, :approved, :summary, :preview_image_id, :category)
end
def find_post
#post = Post.friendly.find(params[:id])
# If an old id or a numeric id was used to find the record, then
# the request path will not match the post_path, and we should do
# a 301 redirect that uses the current friendly id.
if params[:action] == 'show' && request.path != post_path(#post)
return redirect_to #post, :status => :moved_permanently
end
end
end
And, my post.rb
class Post < ActiveRecord::Base
extend FriendlyId
friendly_id :slug_candidates, use: [:slugged, :history]
belongs_to :preview_image, class_name: 'Ckeditor::Picture'
belongs_to :author, class_name: 'User'
## Validations
validates :contents, presence: true
validates :title, presence: true
validates :social_title, presence: true
validates :summary, presence: true, length: 1..300
validates :author, presence: false
validates :category, presence: true
delegate :full_name, to: :author, prefix: true, allow_nil: false
## Instance Methods
def slug_candidates
[
:slug_title,
[:id, :slug_title]
]
end
def slug_title
title&.downcase
end
def should_generate_new_friendly_id?
title_changed?
end
def raw_post
self.contents.html_safe
end
def preview_image_thumb(dimensions = '100x')
preview_image.try(:data).try(:thumb, dimensions).try(:url)
end
def self.preview_image_dimensions
'350x'
end
end
Is there a way to skip this error message? I did some research and found begin/rescue. But I don't know how and where to put it.
It would really appreciate any help or advice.

Answer 1

This is because you are using + to implicitly concatenate the URL to your host, but at least for one post, #post.preview_image.try(:data).try(:url) is returning as nil.
You could fix it by using string interpolation like this:
%meta{:content => "https://www.joynus.com#{#post.preview_image.try(:data).try(:url)}", :name => "twitter:image"}
Or by explicitly converting to string with to_s like this:
%meta{:content => "https://www.joynus.com"+#post.preview_image.try(:data).try(:url).to_s, :name => "twitter:image"}