How do I overwrite every fifth instance of an element in an array in rails?

Question

I'll start by saying that I'm new to rails. This question is for a class I'm currently taking. The lesson topic is CRUD, and the content is a db that stores posts along with their titles and comments.

The instructions are as follows:

Overwrite the title of every fifth instance of Post with the text "CENSORED".

This is my controller:

class PostsController < ApplicationController

  def index

  @posts = Post.all
  end

  def show
  end

  def new
  end

  def edit
  end
end

This is my view file:

<h1>All Posts</h1>

<% @posts.each do |post| %>

    <div class="media">
      <div class="media-body">
        <h4 class="media-heading">
          <%= link_to post.title, post %>
        </h4>
      </div>
    </div>
<% end %>

This is my model:

class Post < ActiveRecord::Base
  has_many :comments
end

I'm not really sure where to even start and would really appreciate any help at all. A point in the right direction would be great. Thanks.

Is this overwrite in the database sense, or overwrite in the view sense? — Makoto, Aug 24 '15 at 04:25
Just in the view sense, they just wanted posts that might have bad language to show "censored", not to change the post itself. — JonMalis, Aug 24 '15 at 16:25

Rajesh Omanakuttan · Accepted Answer · 2015-08-24T06:07:35.637

1

@posts = Post.all
@posts.each_with_index do |post, index| 
  if index % 5 == 4 # since index starts at 0, every 5th object will be at positions 4, 9, 14, 19 etc.
    # Do the change on post object
    post.update_attributes(title: 'CENSORED')
  end
end

edited Aug 24 '15 at 06:07

answered Aug 24 '15 at 04:44

Rajesh Omanakuttan

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Thanks a lot @Rajesh Omanakuttan! I was trying `if post % 5`... This makes sense and works perfectly. – JonMalis Aug 24 '15 at 16:30

Cary Swoveland · Answer 2 · 2015-08-24T06:52:13.017

1

Here are a couple of ways, where @posts = Post.all, and assuming the first post is to be censored:

#1

e = [[:CENSOR] + [:PUBLISH]*4].cycle
  #=> #<Enumerator: [[:CENSOR, :PUBLISH, :PUBLISH, :PUBLISH, :PUBLISH]]:cycle>    
@posts.each {|p| p.update_attributes(title: 'CENSORED') if e.next==:CENSOR }

#2

(0...@posts.size).step(5) {|i| @posts[i].update_attributes(title: 'CENSORED')}

edited Aug 24 '15 at 06:52

answered Aug 24 '15 at 06:45

Cary Swoveland

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score 0 · Answer 3 · answered Aug 24 '15 at 04:20

0

Use each_with_index instead of each; if the index modulo 5 is zero, censor it.

answered Aug 24 '15 at 04:20

Amadan

191,408
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1

`index % 5 == 0` will yield unexpected results. In particular, the first item will be censored too. – Sergio Tulentsev Aug 24 '15 at 06:13
@SergioTulentsev: Not unexpected to me. OP just said every fifth, without specifying which one should be the first censored one. Also, it is trivial to offset, and OP should be able to deduce how. (Actually, someone already posted it, so...) – Amadan Aug 24 '15 at 06:17

score 0 · Answer 4 · answered Aug 24 '15 at 04:21

0

If the intent is to display "CENSORED" for every fifth element, then I'd take a look at each_with_index: http://apidock.com/ruby/Enumerable/each_with_index

answered Aug 24 '15 at 04:21

kevinthompson

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score 0 · Answer 5 · answered Aug 24 '15 at 04:26

0

If @posts is in array form

@posts.each_with_index do |post,index|
  post.update!(title: "CENSORED") if index % 5 == 0
end

OR

If @posts is in your database

@posts.each do |post|
  post.update!(title: "CENSORED") if (post.id % 5 == 0)
end

answered Aug 24 '15 at 04:26

tomtom

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This assumes that id is integer. And id sequence doesn't have holes. – Sergio Tulentsev Aug 24 '15 at 06:12

How do I overwrite every fifth instance of an element in an array in rails?

5 Answers5