I&#39;m trying to follow instructions from the book &quot;Head First Rails&quot; and on page 50 it says to create a model but I am unable to create a model using the rails command.

When I type this at this prompt: localhost:~ home$

     rails generate model ad name:string description:text price:decimal seller_id:integer email:string img_url:string

I get this:

    Usage:
      rails new APP_PATH [options]
    
    Options:
      -r, [--ruby=PATH]              # Path to the Ruby binary of your choice
                                     # Default: /Users/home/.rvm/rubies/ruby-1.9.3-p125/bin/ruby
      -b, [--builder=BUILDER]        # Path to a application builder (can be a filesystem path or URL)
      -m, [--template=TEMPLATE]      # Path to an application template (can be a filesystem path or URL)
          [--skip-gemfile]           # Don&#39;t create a Gemfile
          [--skip-bundle]            # Don&#39;t run bundle install
      -G, [--skip-git]               # Skip Git ignores and keeps
      -O, [--skip-active-record]     # Skip Active Record files
      -S, [--skip-sprockets]         # Skip Sprockets files
      -d, [--database=DATABASE]      # Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db/sqlserver/jdbcmysql/jdbcsqlite3/jdbcpostgresql/jdbc)
                                     # Default: sqlite3
      -j, [--javascript=JAVASCRIPT]  # Preconfigure for selected JavaScript library
                                     # Default: jquery
      -J, [--skip-javascript]        # Skip JavaScript files
          [--dev]                    # Setup the application with Gemfile pointing to your Rails checkout
          [--edge]                   # Setup the application with Gemfile pointing to Rails repository
      -T, [--skip-test-unit]         # Skip Test::Unit files
          [--old-style-hash]         # Force using old style hash (:foo =&gt; &#39;bar&#39;) on Ruby &gt;= 1.9
    
    Runtime options:
      -f, [--force]    # Overwrite files that already exist
      -p, [--pretend]  # Run but do not make any changes
      -q, [--quiet]    # Suppress status output
      -s, [--skip]     # Skip files that already exist
    
    Rails options:
      -h, [--help]     # Show this help message and quit
      -v, [--version]  # Show Rails version number and quit
    
    Description:
        The &#39;rails new&#39; command creates a new Rails application with a default
        directory structure and configuration at the path you specify.
    
        You can specify extra command-line arguments to be used every time
        &#39;rails new&#39; runs in the .railsrc configuration file in your home directory.
    
        Note that the arguments specified in the .railsrc file don&#39;t affect the
        defaults values shown above in this help message.
    
    Example:
        rails new ~/Code/Ruby/weblog
    
        This generates a skeletal Rails installation in ~/Code/Ruby/weblog.
        See the README in the newly created application to get going.
    localhost:~ home$ 

I am using Rails -v 3.2.8
and Ruby 1.9.3p125

rails generate model

Are the two commands equivalent? If not, what&#39;s the difference?

What is the difference between Rails.cache.clear and rake tmp:cache:clear?

I&#39;m using Rails 3.2 and have a migration that contains the code:

    add_column :users, :gift_aid, :integer, :default =&gt; 2
    # reset columns
    User.reset_column_information

    ... code here to load legacy data from sqlite3 database ...
    
    # now create a user with the loaded column data
    user = User.create( ...other cols..., 
                        :gift_aid =&gt; migrated_gift_aid_column_data,
                        ...other cols... )

and I get `unknown attribute: gift_aid` when running the migration. `User.column_names` shows the same list before and after the call to `reset_column_information`. 

Oddly when I manually drop the column in mysql and re-run the migration it works as expected. Starting from the first migration again with an empty database and it doesn&#39;t work so it&#39;s something to do with running all the migrations rather than the single one.

I have a couple of previous migrations on User model, both include `reset_column_information` and both work fine. 

I&#39;m really scratching my head on this one - anyone got any ideas


Model.reset_column_information does not reload columns in rails migration

I have a model with a `belongs_to` association:

    class Car &lt; ActiveRecord::Base
      belongs_to :vendor
    end

So I can call `car.vendor`. But I also want to call `car.company`! So, I have the following:

    class Car &lt; ActiveRecord::Base
      belongs_to :vendor
      def company
        vendor
      end
    end

but that doesn&#39;t solve the assignment situation `car.company = &#39;ford&#39;`, so I need to create another method for that. Is there a simple `alias` mechanism I can use for associations? Can I just use `alias_method :company, :vendor` and `alias_method :company=, :vendor=`?



Possible to alias a belongs_to association in Rails?

I have read few posts regarding `NaN` but did not figure out how to deal with it in Ruby on Rails. I want to check a value if it is a `NaN` I want to replace it with Zero(0).
I tried the following 

    logger.info(&quot;.is_a? Fixnum #{percent.is_a? Fixnum}&quot;)

when percent has `NaN` it returns me false. 

I have made few changes in the logger

    logger.info(&quot;Fixnum #{percent.is_a? Fixnum} percent #{percent}&quot;)

Output

    Fixnum false percent 94.44444444444444
    Fixnum false percent NaN
    Fixnum false percent 87.0


ruby on rails how to deal with NaN

I have 2 models as describes below.

    class EmpGroup &lt; ActiveRecord::Base
      belongs_to :user
      has_many :emp_group_members, dependent: :destroy
    end


and 

    class EmpGroupMember &lt; ActiveRecord::Base
      belongs_to :emp_group
      belongs_to :user
    end

now the problem is whenever I tried to destroy a group then I received a error as below.

    PG::ForeignKeyViolation: ERROR:  update or delete on table &quot;emp_groups&quot; violates foreign key constraint &quot;fk_rails_bd68440021&quot; on table &quot;emp_group_members&quot;
    DETAIL:  Key (id)=(1) is still referenced from table &quot;emp_group_members&quot;.

What I&#39;m missing?

Rails: How to use dependent: :destroy in rails?

I use RVM, the [Ruby Version Manager](https://rvm.io/) to specify a Ruby version and a set of gems for each of my Rails projects.

I have a `.rvmrc` file to automatically select a Ruby version and gemset whenever I `cd` into a project directory.

After installing RVM 1.19.0, I get a message

&gt; You are using `.rvmrc`, it requires trusting, it is slower and it is
&gt; not compatible with other ruby managers, you can switch to
&gt; `.ruby-version` using `rvm rvmrc to [.]ruby-version` or ignore this
&gt; warnings with `rvm rvmrc warning ignore
&gt; /Users/userName/code/railsapps/rails-prelaunch-signup/.rvmrc`,
&gt; `.rvmrc` will continue to be the default project file in RVM 1 and RVM
&gt; 2, to ignore the warning for all files run `rvm rvmrc warning ignore
&gt; all.rvmrcs`.

Should I continue using my `.rvmrc` file or should I switch to a `.ruby-version` file? Which is optimal? What are the ramifications?


Use rvmrc or ruby-version file to set a project gemset with RVM?

When I am starting rails server using `rails s` command it is showing `A server is already running. Check C:/Sites/folder/Pids/Server.pids`

When I open the file it is outputting a 4 digit number only so how could I resolve this issue ? 

**FYI**

 1. No other instance of Rails cmd is running this time.
 2. Checked Task manager but only `cmd.exe` is showing no else process is running. (using Windows).


Server is already running in Rails

I was reading a book and in a chapter about Controllers when it talks about rendering stuff, for JSON it has an example like this but doesn&#39;t go in to details so I couldn&#39;t figure out the bigger picture that this example fits in:

    render :json =&gt; @projects, :include =&gt; tasks


And also some example with JSONP using it with callback functions:

    render :json =&gt; @record, :callback =&gt; &#39;updateRecordDisplay&#39;

Can someone explain these?

Rendering JSON in controller

I want to display a label in `form_for`:

    &lt;div class=&quot;field&quot;&gt;
      &lt;%= f.label :name %&gt;&lt;br /&gt;
      &lt;%= f.text_field :name %&gt;
    &lt;/div&gt;

This generates the label &quot;Name&quot;, but I want it to be &quot;Your Name&quot;. How can I change it?

Rails: Custom text for rails form_for label

I am running Rails 3.2.3, Ruby 1.9 under Fedora 17.  I get this warning, when I run `rails s`, and how do I fix?

&gt;    SECURITY WARNING: No secret option provided to Rack::Session::Cookie.
&gt;    This poses a security threat. It is strongly recommended that you
&gt;    provide a secret to prevent exploits that may be possible from crafted
&gt;    cookies. This will not be supported in future versions of Rack, and
&gt;    future versions will even invalidate your existing user cookies.

No secret option provided to Rack::Session::Cookie warning?

I have a link that I need to submit a post request with. Normally, I&#39;d use jQuery and prevent the link&#39;s default behavior and then submit a form to the destination. This seems like something Rails should be able to help me out with. Sure enough, the `link_to` method has an option for specifying a POST http method:

    link_to &quot;Profile&quot;, &#39;http://example.com/profile&#39;, method: :post

That works, but I need to add 2 parameters too. I tried:

    link_to &quot;Profile&quot;, &#39;http://example.com/profile&#39;, method: post, param1: &#39;value1&#39;, param2: &#39;value2&#39;

That just added those parameters to the `&lt;a&gt;` HTML element, but didn&#39;t submit those when clicking the link:

    &lt;a rel=&quot;nofollow&quot; param1=&quot;value1&quot; param2=&quot;value2&quot; data-method=&quot;post&quot; href=&quot;http://example.com/profile&quot;&gt;Profile&lt;/a&gt;

Is there a way to do a POST request with parameters using `link_to` or any other Rails method? I&#39;m using Rails 3.2.9.

Using Rails link_to for links that post

I want to populate a new feature with dummy data, but don&#39;t want to use the db/seeds.rb file as it already has seeds other data irrelevant for this feature.

To run the default `seeds.rb` file, you run the command `rake db:seed`. 

**If I create a file in the `db` directory called `seeds_feature_x.rb`, what would the rake command look like to run (only) that file?**

Adding a custom seed file

I have some Ruby methods certain (or all) controllers need. I tried putting them in `/app/helpers/application_helper.rb`. I&#39;ve used that for methods to be used in views. But controllers don&#39;t see those methods. Is there another place I should put them or do I need to access those helper methods differently?

Using latest stable Rails.

Where to put Ruby helper methods for Rails controllers?

For the past 2 hours, I have been trying to debug a weird issue in devise which is not letting me login.

Here&#39;s the stuff I&#39;m referring too:


    password 
    =&gt; &#39;vinodsobale&#39;
    
    password == &#39;vinodsobale&#39;
    =&gt; true
    
    resource.valid_password?(password)
    
    =&gt; false
    
    resource.valid_password?(&#39;vinodsobale&#39;)
    
    =&gt; true

    
Attaching the screenshot as well:

     


[![enter image description here][1]][1]
    Note: I have enabled debugger inside devise so the above code is devise internal code.

To me, it looks like a issue in `Devise.secure_compare`.

  [1]: http://i.stack.imgur.com/ywzzP.png

Weird issue with devise valid_password?

I&#39;ve recently upgraded my Rails to v3.2.  The server starts and works, however I&#39;m noticing the following warning:

    Rack::File headers parameter replaces cache_control after Rack 1.5.

In my development.rb I have the following configuration for cache control:

    config.static_cache_control = &quot;public, max-age=36000&quot;

What does the warning mean and what should I do to address it?


Rails emits warning: &quot;Rack::File headers parameter replaces cache_control after Rack 1.5&quot;

I wanted to add confirmation message on link_to function with Ruby.

    = link_to &#39;Reset message&#39;, :action=&gt;&#39;reset&#39; ,:confirm=&gt;&#39;Are you sure?&#39;

Any ideas why it&#39;s not working? 


 

How to add confirm message with link_to Ruby on rails

I have the following code in a Rails controller:

    flash.now[:notice] = &#39;Successfully checked in&#39;
    redirect_to check_in_path

Then in the /check_in view:

    &lt;p id=&quot;notice&quot;&gt;&lt;%= notice %&gt;&lt;/p&gt;

However, the notice does not show up. Works perfect if I don&#39;t redirect in the controller:

    flash.now[:notice] = &#39;Successfully checked in&#39;
    render action: &#39;check_in&#39;

I need a redirect though... not just a rendering of that action. Can I have a flash notice after redirecting?

How to display a Rails flash notice upon redirect?

It is easily possible to remove a column using rails migration.


    class SomeClass &lt; ActiveRecord::Migration
      def self.up
        remove_column :table_name, :column_name
      end
    end

I want to know if there is any way to remove a column from table using console.


How can i remove a column from table using rails console

I have a download link in my app from which users should be able to download files which are stored on s3. These files will be publicly accessible on urls which look something like

    https://s3.amazonaws.com/:bucket_name/:path/:to/:file.png

The download link hits an action in my controller:

    class AttachmentsController &lt; ApplicationController
      def show
        @attachment = Attachment.find(params[:id])
        send_file(@attachment.file.url, disposition: &#39;attachment&#39;)
      end
    end

But I get the following error when I try to download a file:

    ActionController::MissingFile in AttachmentsController#show
    
    Cannot read file https://s3.amazonaws.com/:bucket_name/:path/:to/:file.png
    Rails.root: /Users/user/dev/rails/print
    
    Application Trace | Framework Trace | Full Trace
    app/controllers/attachments_controller.rb:9:in `show&#39;

The file definitely exists and is publicly accessible at the url in the error message.

How do I allow users to download S3 files?

Using send_file to download a file from Amazon S3?

I have read it from the Rails guides, Have looked at Micheal Hartel book and now reading it from Rails View book but still I get confused :(

There is a `_footer.html.erb`  file so it is a &quot;partial&quot;  and in the code it has written:

    &lt;%=render &#39;layouts/footer&#39; %&gt;

so my understanding is that when it sees this, goes and insert the HTML for footer file in here. Ok...
Now a few pages later it is saying:

    &lt;%= render partial: &#39;activitiy_items/recent&#39; %&gt;

so WHY this time we have the word &quot;partial&quot; in here but we didn&#39;t have it in the previous one?

And there somewhere else I see `&lt;%= yield :sidebar %&gt;`

So this `yield` also insert HTML in its place? Well wasn&#39;t it what `render` was doing? 

I was hoping if another programmer instead of books explains this to me maybe I get it this time:)

Difference between Render and Render Partial and Yield

I am using rails 3.2 and i have to set a background for one of the page and i have tried many ways and nothing went right, so looking for some good help. I have tried 

    background: url(&lt;%= asset_path &#39;background.jpg&#39; %&gt;)
    
    background: url(&quot;public/background.jpg&quot;);
    
    background-image:url(&#39;/assets/images/background.jpg&#39;)

and nothing worked. Please help me.

Rails: How to set a background image in rails from css?

I take naming pretty seriously, so I think pretty hard about good names for my ActiveRecord models. However, I frequently come up with a name and it has some conflict with a reserved name, either in the database or Ruby or Rails. Model or field names like `set` or `group`. Sometimes the issue isn&#39;t immediately apparent either. Is there a list somewhere of names we can&#39;t use in our model names and a list for field names?

All Ruby on-Rails-3.2 Solutions on Gang of Coders

Total of 23 Ruby on-Rails-3.2 Solutions