update attribute for rails model

Question

In my app, I'm trying to make admin user can edit one attribute of a "post"

The post model is:

class PostsController < ApplicationController

before_filter :admin_user,   only: [:edit, :update]

def edit
  @post = Post.find(params[:id])
end

def update
  @post = Post.find(params[:id])
  if @post.update_attributes(params[:post][:some_attr])
     flash[:success] = "Post updated"
     redirect_to posts_path
  else
    redirect_to root_path
  end
end

The edit view is :

  <% provide(:title, "Edit post") %> 
  <h1>Update the post</h1>

  <div class="row">
    <div class="span6 offset3">
    <%= form_for(@post) do |f| %>
        <%= f.label :some_attr %>
        <%= f.text_field :some_attr %>

    <%= f.submit "Save changes", class: "btn btn-large btn-primary" %>
   <% end %>

When I try to input "123" in the some_attr test_field in edit page, it renders error:

NoMethodError in PostsController#update

undefined method `stringify_keys' for "123":String


Application Trace | Framework Trace | Full Trace
app/controllers/posts_controller.rb:22:in `update'
Request

Parameters:

{"utf8"=>"✓",
 "_method"=>"put",
 "authenticity_token"=>"EdTg+cFBnZY447oSDqSTPfb/PJ6VisJOrQ8kvichDrE=",
 "post"=>{"some_attr"=>"123"},
 "commit"=>"Save changes",
 "id"=>"17"}

What could be the problem? Which piece of the puzzle am I missing?

Thanks

Kevin Bedell · Accepted Answer · 2012-05-19 02:53:02Z

2

I believe this line:

@post.update_attributes(params[:post][:some_attr])

should read like this:

@post.update_attributes(params[:post])

To perform an update to @post, you need to pass in the entire hash of attributes for it -- not just the one you're changing.

Good luck!

answered May 19, 2012 at 2:53

Kevin Bedell

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1 Comment

alexZ Over a year ago

Thanks! That's right..I should do more researching before ask

x1a4 · Accepted Answer · 2012-05-19 02:53:12Z

1

The problem is this line:

 if @post.update_attributes(params[:post][:some_attr])

params[:post][:some_attr] is just a value. A field is not specified. If you change the line to

 if @post.update_attributes(params[:post])

the attribute should update as expected.

answered May 19, 2012 at 2:53

x1a4

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2 Comments

alexZ Over a year ago

Thanks! That solved my problem! Actually update_attributes is expecting a hash instead of a string

x1a4 Over a year ago

Yep, exactly. You can pass in an entire hash of attributes to update. Here is some documentation on update_attributes if you're curious.

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