Rails 4 - Paths - update action

Question

I am trying to make an app in Rails 4.

I have an articles model.

The show page includes a button which is supposed to be a link to an edit (update) method.

I have:

 <%= button_to 'Edit', articles_path(article), :method => :update, :class => 'btn btn-large btn-primary' %>

When I try this, I get this error:

NameError in Articles#show Showing //app/views/articles/show.html.erb where line #49 raised:

undefined local variable or method `article' for #<#:0x007fe14dc83030>

Line 49 has the button to edit.

Can anyone see what's wrong?

My show page has:

<div class="col-xs-2">
            <%= image_tag @article.image.thumb.url if @article.image?  %>
        </div>
        <div class="col-xs-10">
            <div class="articletitle">
                <%= @article.title %>
            </div>    
            <div class="commentattributionname">
                <%= @article.user.try(:full_name) %>
            </div>
            <div class="commentattributiontitle">
                <%= @article.user.try(:formal_title) %>
            </div>
            <div class="commentattributiondate">
                <%= @article.created_at.try(:strftime, '%e %B %Y') %>
            </div>

        </div>
    </div>

    <div class="row">
        <div class="col-sm-9">
            <div class="intpol3" style="text-align: left; margin-left:60px; padding-top:50px">
               <%= safe_join(@article.body.split("\r\n"), "<br />".html_safe) %>
            </div>
        </div>  
        <div class="col-sm-3">
        <!-- placeholder for tags -->
        </div>  

    </div>

     <!-- if @article.user.full_name.present?  -->
       <!-- <div class="indexsubtext"> @article.user.full_name </div> -->
     <!-- end  -->
     <div class="row">
        <div class="col-xs-8">
        </div>
        <div class="col-xs-4">
            <div class="formminor" style="margin-bottom:5%">
                <% if policy(@article).update? %>
                 <%= button_to 'Edit', articles_path(article), :method => :update, :class => 'btn btn-large btn-primary' %>
                <% end %> 
                  |
                <%= link_to 'More from the blog', articles_path %>
            </div>
        </div>        
    </div>

My articles controller has:

class ArticlesController < ApplicationController
  before_action :set_article, only: [:show, :edit, :update, :destroy]
def set_article
      @article = Article.find(params[:id])
      authorize @article
    end

My routes have:

resources :articles do
    collection do 
      get 'search' 
    end
    resources :comments, module: :articles
  end

If I change it to:

<%= button_to 'Edit', articles_path(article), :method => :update, :class => 'btn btn-large btn-primary' %>

I get this error:

ActionController::ParameterMissing in ArticlesController#create
param is missing or the value is empty: article

My controller has:

def create
    # before_action :authenticate_user!
    # authorize @article
    @article = current_user.articles.new(article_params)

    respond_to do |format|
      if @article.save
        format.html { redirect_to(@article) }
        format.json { render :show, status: :created, location: @article }
      else
        format.html { render :new }
        format.json { render json: @article.errors, status: :unprocessable_entity }
      end
    end
  end

def article_params
      params.require(:article).permit(:body, :title, :image, :tag_list,
        comment_attributes: [:opinion])
    end

TAKING TAGLIA'S SUGGESTION

I get this error:

ActionController::ParameterMissing in ArticlesController#create
param is missing or the value is empty: article

Answer 1

This means you've not defined article anywhere in your controller. You need to define the variable article = Article.find(params: [:id]) or similar in your Articles show action, that way you should be able to find the article you need.

Answer 2

If you have used resources :articles to generate the routes for your articles, rails provide you a specific helper to access the edit action. This should work:

 <%= button_to 'Edit', edit_article_path(@article), :class => 'btn btn-large btn-primary', method: :get %>

Your code had two problems:

1. articles_path is a helper which generates the path to the index action, and does not require any arguments;
2. "update" is not a valid HTTP verb: you can only use GET, POST, PATCH, PUT, and DELETE. The correct verb for an update action is PATCH (or PUT), still you should use a simple GET to display an edit form as there is no model update at that stage.