Flowdock

Notes posted to Ruby on Rails

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February 19, 2014
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Rendering JSONP

If you provide the :callback option with a nil value, then the default JSON object will be returned. As such, this makes creating JSONP response from the render syntax very easy in your controllers, like so:

render json: @object, callback: params[:jsoncallback]
February 3, 2014
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Symbols more performant than strings

>> options_from_collection_for_select(@posts, :slug, :title, params[:slug])

Consider using symbols for performance, otherwise it will generate a string each time instead of a symbol which will reference the same object.

January 16, 2014
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Storing array values

I tried to add a array value using hidden_field_tag and access it in jquery. It just returns the flattened version of array. eg:(If i try to store [1,[1,2,3]] in hidden_field_tag , in jquery iam just getting ‘1 1 2 3’) but if i use input field with type=hidden iam getting the correct value. Why is that?

January 12, 2014
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using hash as order

order can be specified as a hash, e.g.:

order(id: :desc)

This will prevent “ambiguous column” errors when the order is used with joins or includes.

January 9, 2014 - (v3.2.13)
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onChange Event

Hello,

I’m brand new to ROR and in general server side programing. I’m a iOS developer who is trying to learn ROR.

I’m trying to use collection select to implement filtering for my page. The idea is there are a bunch of posts and I want to implement record filtering for those.

The first collection box would have parameters like “Date”, “Amount”, “Category” and based on the selection of this a secondary drop down would appear and allow the user to make a selection. The records on this page would be then filtered based on both the selection.

I have been trying out many things and have googled a lot on collection but I have reached a dead end now. I’m pretty new and just started learning ROR.

You help is much appreciated here.

Thanks in advance.

Note: the code below might be wrong and as of now its not even compiling.. currently it complaints of “remote_function” not defined…


I have a page that looks like this,

<div class=“span8”>

<% if @user.spendings.any? %>

    <h3> Spendings (<%= @user.spendings.count  %>)</h3>

    <%= collection_select(:category, :category, Category.all, :id, :name, 

{:prompt => 'Select'})%>

<%= collection_select :event, :filterType, Filters.all, :id, :filterType, {},

  {

  :onchange => remote_function(

    :url => {:action => "updatelevel", :controller => "Spendings", :id => 1},

    :with => "'level_id='+this.value"

  )}

%>

      <ol class="spendings">

        <%= render @spendings %>

      </ol>

      <%= will_paginate @spendings %>

  <% end %>

</div>
January 8, 2014 - (v3.0.0 - v3.2.13)
2 thanks

An Example for using it.

Call it in a before filter in your Base or Application Controller.

before_filter :authenticate_through_api_client

def authenticate_through_api_client

# this block should return true or false
authenticate_or_request_with_http_token |token,other_options|
 Apiclient.find_by_client_key(token).present?
end

end

# Sample request type: it expects a token in headers as

Authorization:Token token=“your_token_goes_here”

Authorization is the key and Token token=“” is value

December 16, 2013
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Placing it within stack at certain level

where_you_want_it = 0 (begining of stack loaded first) Rails.application.config.middleware.insert_before(where_you_want_it, Module::Class)

December 6, 2013
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Update the uniqueness field when it value dependent on another existent field without uniqueness restriction.

I’m using sub-transaction to update existent records on DB. I use this approach to update the uniqueness field when it value dependent on another existent field without uniqueness restriction.

Migration for uniqueness with existent dependent data in DB

class AddUniquenessBarToFoo < ActiveRecord::Migration
  class Foo < ActiveRecord::Base
  end

  def change

    add_column :foos, :bar, :string
    execute "ALTER TABLE foos ADD CONSTRAINT uk_foods_bar UNIQUE (bar)"    

    Foo.reset_column_information
    Foo.all.each do |f|
      begin
        #try get unique value in a new sub-transaction
        Foo.transaction(requires_new: true) do
          f.update_attributes!(:bar => "some ops. with another non-unique existent field to set this")
        end
      rescue ActiveRecord::StatementInvalid
         #We can't reuse a crashed transaction. New one.
         Foo.transaction(requires_new: true) do
          #Alternative unique value, if another error exist it's another
          #migration problem and then raise new error.
          f.update_attributes!(:bar => "some operation to set this-#{f.id}")
        end
      end
    end   
    change_column :foos, :bar, :string, :null => false

  end
end

Be aware about performance that is transaction per record for big DB.

December 6, 2013
0 thanks

Migration for uniqueness with existent data in DB

I’m using sub-transaction to update existent records on DB. I use this approach to update the uniqueness field when it value dependent on another existent field without uniqueness restriction.

Migration for uniqueness with existent dependent data in DB

class AddUniquenessBarToFoo < ActiveRecord::Migration
  class Foo < ActiveRecord::Base
  end

  def change

    add_column :foos, :bar, :string
    execute "ALTER TABLE foos ADD CONSTRAINT uk_foods_bar UNIQUE (bar)"    

    Foo.reset_column_information
    Foo.all.each do |f|
      begin
        #try get unique value in a new sub-transaction
        Foo.transaction(requires_new: true) do
          f.update_attributes!(:bar => "some ops. with another non-unique existent field to set this")
        end
      rescue ActiveRecord::StatementInvalid
         #We can't reuse a crashed transaction. New one.
         Foo.transaction(requires_new: true) do
          #Alternative unique value, if another error exist it's another
          #migration problem and then raise new error.
          f.update_attributes!(:bar => "some operation to set this-#{f.id}")
        end
      end
    end   
    change_column :foos, :bar, :string, :null => false

  end
end

Be aware about performance that is transaction per record for big DB.

December 3, 2013
0 thanks

usage examples

For detailed usage examples of where see “Conditions” under ActiveRecord::Base.

December 2, 2013 - (v3.2.13)
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Redirect Status

Redirect 302

get "/accounts", :to => redirect("/", :status => 302)
November 26, 2013
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Updated list of statuses

The list of supported statuses is now in the layout & rendering rails guide:

http://guides.rubyonrails.org/layouts_and_rendering.html#the-status-option

November 22, 2013
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November 18, 2013
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BEWARE of options[:value] in a partial

No problem with new records however,

the following line will not display the current @ecard value on EDIT but ‘contact@host.com’.

text_field :ecard, :sender, :value => 'contact@host.com'

Don’t let your views take control, but if you insist:

text_field :ecard, :sender, :value => f.object.ecard.blank? ? 'contact@host.com' : f.object.ecard

This doesn’t make sense, since when this object was created they deleted the default, which made it blank. Why would they want it back?

November 13, 2013 - (v3.2.13)
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Adjacency

Just for completeness (it should behave like this), comparing ranges that start and end with the same value will overlap, e.g.

(1..5).overlaps?(5..10) # => true
November 13, 2013 - (v3.2.13)
0 thanks

Take care with time ranges

Trying this in the console:

(1.day.from_now..5.days.from_now).overlaps?(5.days.from_now..10.days.from_now)

will blow up…

It’s fine with Dates though:

(1.day.from_now.to_date..5.days.from_now.to_date).overlaps?(5.days.from_now.to_date..10.days.from_now.to_date) # => true
November 8, 2013
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submit button with rails javascript's onclick event handler method

Code example

<%= f.submit ‘Create User’, class: ‘buttons’, :onclick => “validate_user_form_and_submit()” %>

November 7, 2013
1 thank

Correction

Where you see:

HelperData.new(datetime, options, html_options).select_hour

The correct would be:

HelperDate.new(datetime, options, html_options).select_hour

Class name and class instance must be same name.

Code works fine in Rails 3.2.13.

November 5, 2013
0 thanks

The "instance-level equivalent" ActiveRecord::Base#increment is NOT atomic

Typically, you want to increment counters atomically, so the class method ActiveRecord::Base.increment_counter is the right choice.

Also, there is an issue with the increment example below as it does not save automatically:

item = Item.find(1)
item.foo_count # => 0
item.increment(:foo_count)
item.foo_count # => 1
item.reload
item.foo_count # => 0
item.increment(:foo_count)
item.save
item.reload
item.foo_count # => 1
October 21, 2013 - (v2.3.8)
1 thank

Found out you can't set the type to number

I am sure others have tried to do this but I thought I would add a not that tells ever one. You can’t use the type field in in rails 2.3. It is always set back to type => “text”

So if you are trying to set it to type => “number” it will not work. It always goes back to text. Sorry only way around this is to use a text_field_tag and set the type in that.

<%= text_field_tag :thing, type: "number" %>

Code above is the only way to set the type. in rails 3 you can just call number_field and it will work

October 16, 2013
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Erb tags

The <% -%> is not being used since Rails 3.

The example above should be changed to:

<%= form_tag('/posts') do %>
  <div><%= submit_tag 'Save' %></div>
<% end %>
October 11, 2013 - (<= v3.2.13)
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Bug - this is not working as documented

The stacking of several after_commit lines is not working. The last line overwrites the ones before.

Using an array for the :on options is also not working.

For details look here: http://github.com/rails/rails/issues/988#issuecomment-12653474

October 10, 2013
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Classy guys...

:fav_bra_size - really?

October 2, 2013
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You have explain well

You have explain well about fragment caching as I was in need of this information. http://autobodycarparts.com

October 2, 2013
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Statistics

Thanks for the coding part it was really helpful for me, I would apply it on my project. http://www.koolchart.com

October 1, 2013
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Update multiple attributes with raw sql

You can update multiple attributes with sql for each record being updated by using the following syntax:

example

Model.update_all("foo = 'bar', baz = 'bat'")
September 24, 2013
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Missing documentation for options hash

The deprecated function (http://apidock.com/rails/ActiveRecord/Serialization/to_json) has more useful documentation for the options hash.

September 13, 2013
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Edge case

NilClass#try doesn’t check for methods on itself:

nil.blank?        #=> true
nil.try :blank?   #=> nil