From Rails 4 upwards, the index removes automatically with the column removal.

No, unfortunately you have to remove the index manually from within your migration using the [`remove_index`][1] method.

[1]: http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/Table.html#method-i-remove_index

To clarify, inside a migration the syntax to remove a 2 column index is the following

    remove_index :actions, :column =&gt; [:user_id,:action_name]

or by name, a worse option from my point of view

    remove_index :actions, :name =&gt; &quot;index_actions_on_user_id_and_action_name&quot;

Just as a caution, while Rails 4 _will_ remove the index for you if you remove the column, you should specify the column type. Without a column type, running `rake db:rollback` will return 

    rake aborted!
    StandardError: An error has occurred, all later migrations canceled:
    
    remove_column is only reversible if given a type.


I was experimenting with dropping foreign key columns that were indexed. Even specifying `index: true` in the change block didn&#39;t seem to make the columns reversible on rollback.

If you want to remove index you should use `remove_index`, if you use `remove_column` it does remove the index but you can&#39;t run rake db:rollback. As Jim mentioned.

    remove_column is only reversible if given a type.

In Rails &gt; 3.2.16, removing the column removes the index.

This C++ program is a CGI script, I have no desire to deal with exceptions. I&#39;d rather get a marginal performance boost and let the OS (Linux) handle cleanup after the process dies.

I am using the Standard C++ Library, and want any function to `die` like in Perl: **Whenever it throws an exception.** Without unwinding, *or running any further code* in my process.

How does -fno-exceptions work? If I have no catch at all in my code, and basically pretend like exceptions do no exist. but I **do** use std:: c++ library which **can** throw()?

Disabling C++ exceptions, how can I make any std:: throw() immediately terminate?

Is it safe to assume that Windows local and network file paths are NOT case sensitive?

File paths in Windows environment not case sensitive?

In Rails 2, will removing a column with a Rails migration also change/remove indexes associated with the column?  If not, and instead you have to also change/remove each index manually, shouldn&#39;t it instead be automated?

Thanks (from a Rails newbie)

Will removing a column with a Rails migration remove indexes associated with the column

<p>In Rails 2, will removing a column with a Rails migration also change/remove indexes associated with the column?  If not, and instead you have to also change/remove each index manually, shouldn't it instead be automated?</p>
<p>Thanks (from a Rails newbie)</p>


I&#39;m trying to customise a ActiveAdmin form for a Recipe model that has a has_many relationship with Step.

    class Recipe &lt; ActiveRecord::Base
      has_many :steps
    end

    class Step &lt; ActiveRecord::Base
      acts_as_list :scope =&gt; :recipe
      
      belongs_to :recipe
    end

I have the following in my ActiveAdmin file with relation to this:

    form do |f|
      f.has_many :steps do |ing_f|
        ing_f.inputs
      end
    end

The following error is thrown when I try to load the form:
&gt; undefined method `new_record?&#39; for nil:NilClass

I&#39;ve isolated it so far to the has_many method but I&#39;m lost past this. Any advice and help would be appreciated!


ActiveAdmin with has_many problem; undefined method &#39;new_record?&#39;

I have been googling for about 90 minutes now and still don&#39;t have an answer to this.  Where do I set `default_url_options`?  I&#39;ve already set it for `config.action_mailer.default_url_options` to solve this same bug elsewhere, but now I&#39;m getting this error when trying to use a URL helper inside an RSpec spec.  I have no idea where it&#39;s expecting default_url_options to be set.

     Failure/Error: listing_url(listing).should match(/\/\d+-\w+$/)
     RuntimeError:
       Missing host to link to! Please provide :host parameter or set default_url_options[:host]
     # ./spec/routing/listing_routing_spec.rb:9:in `block (3 levels) in &lt;top (required)&gt;&#39;

This code has nothing to do with emails/ActionMailer, it just happens to need a URL instead of a path.

Any ideas?

Rails: Missing host to link to! Please provide :host parameter or set default_url_options[:host]

Rails has built in log filtering so you don&#39;t log passwords and credit cards.  Works great for that but when you want to trigger a custom log (like to email) and send your own params or other data along with it, the parameters are obviously not auto-filtered. I have been digging and trying to find this in the rails source but have had no luck so far.

I have configured rails to filter parameters as follows and it works properly for keeping the data out of rails logs:

    config.filter_parameters += [:password, :password_confirmation, :credit_card]

How would you filter sensitive data from the params hash before dumping it into an email, api call or custom (non-rails) log?


How to filter parameters in rails?

I have an observer and I register an `after_commit` callback.
How can I tell  whether it was fired after create or update?
I can tell an item was destroyed by asking `item.destroyed?` but `#new_record?` doesn&#39;t work since the item was saved.

I was going to solve it by adding `after_create`/`after_update` and do something like `@action = :create` inside and check the `@action` at `after_commit`, but it seems that the observer instance is a singleton and I might just override a value before it gets to the `after_commit`. So I solved it in an uglier way, storing the action in a map based on the item.id on after_create/update and checking its value on after_commit. Really ugly.

Is there any other way?

# Update

As @tardate said, `transaction_include_action?` is a good indication, though it&#39;s a private method, and in an observer it should be accessed with `#send`.

    class ProductScoreObserver &lt; ActiveRecord::Observer
      observe :product

      def after_commit(product)
        if product.send(:transaction_include_action?, :destroy)
          ...

Unfortunately, the `:on` option does not work in observers.

Just make sure you test the hell of your observers (look for `test_after_commit` gem if you use use_transactional_fixtures) so when you upgrade to new Rails version you&#39;ll know if it still works.

(Tested on 3.2.9)

# Update 2

Instead of Observers I now use ActiveSupport::Concern and `after_commit :blah, on: :create` works there.

Rails 3: How to identify after_commit action in observers? (create/update/destroy)

I want to test a file upload in rails, but am not sure how to do this.

Here is the controller code:

    def uploadLicense
        #Create the license object
        @license = License.create(params[:license]) 
        
        
        #Get Session ID
        sessid = session[:session_id]
    
    	puts &quot;\n\nSession_id:\n#{sessid}\n&quot;
        
        #Generate a random string
        chars = (&quot;a&quot;..&quot;z&quot;).to_a + (&quot;A&quot;..&quot;Z&quot;).to_a + (&quot;0&quot;..&quot;9&quot;).to_a
        newpass = &quot;&quot;
        1.upto(5) { |i| newpass &lt;&lt; chars[rand(chars.size-1)] }
        
        #Get the original file name
        upload=params[:upload]
        name =  upload[&#39;datafile&#39;].original_filename 
        
        @license.format = File.extname(name)
        
        #calculate license ID and location
        @license.location = &#39;./public/licenses/&#39; + sessid + newpass + name 
    
        #Save the license file
        #Fileupload.save(params[:upload], @license.location) 
        File.open(@license.location, &quot;wb&quot;) { |f| f.write(upload[&#39;datafile&#39;].read) }
        
         #Set license ID
        @license.license_id = sessid + newpass
        
        #Save the license
        @license.save
        
        redirect_to :action =&gt; &#39;show&#39;, :id =&gt; @license.id 
    end


I have tried this spec, but it doesnt work:

	it &quot;can upload a license and download a license&quot; do
		file = File.new(Rails.root + &#39;app/controllers/lic.xml&#39;)
		license = HashWithIndifferentAccess.new
		license[:datafile] = file
		info = {:id =&gt; 4}
		post :uploadLicense, {:license =&gt; info, :upload =&gt; license}
	end

How can I simulate the file upload, using rspec?

test a file upload using rspec - rails

I need to add timestamps (`created_at` &amp; `updated_at`) to an existing table. I tried the following code but it didn&#39;t work.

    class AddTimestampsToUser &lt; ActiveRecord::Migration
        def change_table
            add_timestamps(:users)
        end
    end

Add timestamps to an existing table

What is the difference between `t.references` and `t.belongs_to`?
Why are we having those two different words? It seems to me they do the same thing?
Tried some Google search, but find no explanation.

    class CreateFoos &lt; ActiveRecord::Migration
      def change
        create_table :foos do |t|
          t.references :bar
          t.belongs_to :baz
          # The two above seems to give similar results
          t.belongs_to :fooable, :polymorphic =&gt; true
          # I have not tried polymorphic with t.references
          t.timestamps
        end
      end
    end


What is the difference between t.belongs_to and t.references in rails?

I&#39;m in the process of adding Devise to an existing Rails app, with a Users table already defined. The devise generator pushed out the following migration:
        
    class AddDeviseToUsers &lt; ActiveRecord::Migration
      def self.up
        change_table(:users) do |t|
   
         ## Database authenticatable
         t.string :email,              :null =&gt; false, :default =&gt; &quot;&quot;
         t.string :encrypted_password, :null =&gt; false, :default =&gt; &quot;&quot;

         ## Recoverable
         t.string   :reset_password_token
         t.datetime :reset_password_sent_at
 
         ## Rememberable
         t.datetime :remember_created_at

         ## Trackable
         t.integer  :sign_in_count, :default =&gt; 0

         blah blah blah....

       end

       add_index :users, :email,                :unique =&gt; true
       add_index :users, :reset_password_token, :unique =&gt; true
     end

The downward migration isn&#39;t generated, and I&#39;m having a heck of a time removing those indexes. I&#39;m seeing different suggested notation in the documentation, and different suggestions online, but none of them seem to be working for me.  For example...

    def self.down
      change_table(:users) do |t|
        t.remove  :email
        t.remove  :encrypted_password
      
        t.remove  :reset_password_token

        blah blah blah...
      end
    
      remove_index :users, :email
      remove_index :users, :reset_password_token
    end

results in...

    An error has occurred, this and all later migrations canceled:

    Index name &#39;index_users_on_email&#39; on table &#39;users&#39; does not exist

which is odd, because if I check the database, sure enough, &#39;index_users_on_email&#39; is right there...  

I&#39;ve tried other variations, including

    remove_index :users, :column =&gt; :email

    remove_index :users, &#39;email&#39;

or:

    change_table(:users) do |t|
      t.remove_index :email
    end

...but no dice. I&#39;m running Rails 3.1.0, Ruby 1.9.2, rake 0.9.2.2, with Postgres.

The command that&#39;s letting me down is:

    bundle exec rake db:rollback STEP=1

after successfully apply the migration up. Any advice?

What&#39;s the correct syntax for remove_index in a Rails 3.1.0 migration?

Looks like the new rails version has &quot;change&quot; versus self.up and self.down methods.

So what happens when one has to roll back a migration how does it know what actions to perform. I have the following method that I need to implement based on an online tutorial:

    class AddImageToUsers &lt; ActiveRecord::Migration
      def self.up
        add_column :users, :image_file_name, :string
        add_column :users, :image_content_type, :string
        add_column :users, :image_file_size, :integer
        add_column :users, :image_updated_at, :datetime
      end
    
      def self.down
        remove_column :users, :image_file_name, :string
        remove_column :users, :image_content_type, :string
        remove_column :users, :image_file_size, :integer
        remove_column :users, :image_updated_at, :datetime
      end    
    end

How can I do the same using the new change method?

Rails migrations: self.up and self.down versus change

This questions stems from: https://stackoverflow.com/questions/11313872/how-to-link-form-after-creating-rails-join-table

I am creating the join table between my Product and Category Models.

What should the join table be named? categories_products or category_products or something else?

Content Type	Original Author	Original Content on Stackoverflow
Question	Dexygen	View Question on Stackoverflow
Solution 1 - Ruby on-Rails	enter08	View Answer on Stackoverflow
Solution 2 - Ruby on-Rails	John Topley	View Answer on Stackoverflow
Solution 3 - Ruby on-Rails	Maragues	View Answer on Stackoverflow
Solution 4 - Ruby on-Rails	Jim	View Answer on Stackoverflow
Solution 5 - Ruby on-Rails	William Hu	View Answer on Stackoverflow
Solution 6 - Ruby on-Rails	Mark Swardstrom	View Answer on Stackoverflow

Will removing a column with a Rails migration remove indexes associated with the column

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File paths in Windows environment not case sensitive?

Disabling C++ exceptions, how can I make any std:: throw() immediately terminate?

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