Flowdock

Notes posted to Ruby on Rails

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March 6, 2016
1 thank

RE: FALSE: Creates record by given attributes only if table is empty

Dino’s comment was almost certainly due to a misunderstanding of the API, a mistake I made myself the first time I used it, and one I’ve witnessed multiple others make as well.

The fact that this method takes an attributes parameter leads one to think the passed params are the criteria for the selection. At first glance it would appear it would be used like this:

User.first_or_create(email: 'derek@somwhere.com')

Where in reality this would grab the “first” record (say w/ email “john@smith.com”), and change its email to “derek@somwhere.com”, a fairly surprising action that doesn’t obviously fail, leading to some pretty subtle bugs.

In reality it should be used like this:

User.where(email: 'derek@somwhere.com').first_or_create

And the attributes param. isn’t used in 99% of use cases. (If at all - the provision for the block that executes only on create fully duplicates what the attributes parameter can do in a much more obvious way.)

IMHO this is simply a bad API that one just needs to be aware of. But it’s unfair to knock dino for what’s likely a highly common misreading.

March 4, 2016 - (>= v4.0.2)
0 thanks

FALSE: Creates record by given attributes only if table is empty

I very much doubt that dino’s comment was ever correct, but it certainly isn’t correct now. The behavior liantics describes is correct.

February 14, 2016
1 thank

Text values for enum

There is way to have text values for enum. It is useful to have localized select options and latin values in database. 1) User model: enum kind: { ‘текст’=>‘text’, ‘изображение’=>‘picture’, ‘звук’=>‘audio’, ‘видео’=>‘video’ } 2) Edit view: <%= select_tag ‘user[kind]’, options_for_select(User.kinds, @user.kind) %>

February 12, 2016 - (<= v4.2.1)
0 thanks

Generate Token

For generate a token, make this:

def generate_token
  self.token = SecureRandom.uuid
end

SecureRandom return a number random and the uuid make this number be unique. This a good idea for use in shopping cart, for example

February 3, 2016 - (v4.0.2 - v4.2.1)
0 thanks

Params of conditions

You can pass an proc for o callback with the conditions

before_action :initial_value, only: [:index, :show], unless: -> { @foo.nil? }

before_action :initial_value, only: [:index, :show], if: -> { @foo }
February 3, 2016 - (v4.0.2 - v4.2.1)
0 thanks

Params of conditions

You can pass an proc for o callback with the conditions

after_action :initial_value, only: [:index, :show], unless: -> { @foo.nil? }

after_action :initial_value, only: [:index, :show], if: -> { @foo }
January 28, 2016
0 thanks

the method to make 'day' disappear.

If you wanna show “year” and “month” only, you can use “order” to do it:

select_date(Date.current, order: [:year, :month])

That’s it.

January 22, 2016
3 thanks

Creates record by given attributes only if table is empty

This method first searches the table for ANY FIRST RECORD, not the one matching given attributes. If no record is found at all, it creates one using the specified attributes. This might be misunderstood in many cases.

January 6, 2016
0 thanks

What about Marshal remote code execution risks?

Good suggestion about using Marshal to avoid cycles, astgtciv, but what about the security risks of doing that?

See http://ruby-doc.org/core-2.2.2/Marshal.html where it states:

By design, ::load can deserialize almost any class loaded into the Ruby process. In many cases this can lead to remote code
execution if the Marshal data is loaded from an untrusted source.

As a result, ::load is not suitable as a general purpose serialization format and you should never unmarshal user supplied input or other
untrusted data.

If you need to deserialize untrusted data, use JSON or another serialization format that is only able to load simple,primitive’ types such
as String, Array, Hash, etc. Never allow user input to specify arbitrary types to deserialize into.
January 3, 2016
0 thanks

Setting HTTP_REFERER

If your integration test is checking for correct behavior of a redirect to the request referer, you can set the referring path in the headers hash with syntax like:

patch update_user_role_path, { user: {role: "vip"} }, { 'HTTP_REFERER' => user_url } 
assert_redirected_to user_url
December 2, 2015
0 thanks

Not quite opposite of new_record?

new_record? will not check if the record has been destroyed

December 2, 2015
1 thank

Not quite opposite of persisted?

persisted? will also check if the record has not been destroyed

November 23, 2015 - (v3.2.13)
0 thanks

Rails 3.2.19

As Jebin reported, we are not getting the value in array format when we set the hidden_field_tag with an Array variable, instead it is a String that we are getting.

November 10, 2015
0 thanks

instead of memoize

See this for deprecated github.com/rails/rails/commit/36253916b0b788d6ded56669d37c96ed05c92c5c

use

def something
  return @_var if defined? @_var
  # more code
end
November 3, 2015 - (v4.2.1)
0 thanks

Possible bug

Works as expected for non bang methods

>  a={x:1, y:2, z:3}                                                                      
=> {:x=>1, :y=>2, :z=>3}

> a.slice(:y)                                                                             
=> {:y=>2}

> a.except(:y)                                                                            
=> {:x=>1, :z=>3}

Bug on slice! it behaves like except!

> a.clone.slice!(:y)                                                                                                                                                                                
=> {:x=>1, :z=>3}

> a.clone.except!(:y)                                                                                                                                                                               
=> {:x=>1, :z=>3}

slice! should return {:y=>2} and modify a to no longer have it

October 19, 2015
0 thanks

Multiple files

To use multiple file upload need to use variable_name[].

like this:

file_field_tag 'files[]', :multiple => true  

and in controller:

if !params[ :files ].nil?
  params[ :files ].each{ |file|
     # do your staff
  }
end
October 13, 2015 - (>= v4.1.8)
0 thanks

"Class methods on your model are automatically available on scopes."

The final example above – “Class methods on your model are automatically available on scopes.” – contains a subtle but vital change from earlier versions of the doc – namely, “pluck” (current example) vs “map” (old example). The former works, the latter does not. See http://github.com/rails/rails/issues/21943 for confirmation that the old documentation is incorrect, and for a workaround.

(Spoiler alert: Use

all.map(&:title)

instead of just

map(&:title)

in order to achieve the same effect.)

October 13, 2015 - (>= v4.1.8)
0 thanks

"Class methods on your model are automatically available on scopes."

The final example above – “Class methods on your model are automatically available on scopes.” – does not work as written. See http://github.com/rails/rails/issues/21943 for confirmation that the old documentation is incorrect, and for a workaround.

(Spoiler alert: Use

all.map(&:title)

instead of just

map(&:title)

in order to achieve the same effect.)

October 5, 2015 - (>= v3.2.1)
0 thanks

arel_table order by

More objected way how to achieve ORDOR BY .… DESC is like this :

class User < ActiveRecord::Base
  has_many :status_changes

  def latest_status_change
    status_changes
     .order(StatusChange.arel_table['created_at'].desc)
     .first
  end
end

class StatusChange < ActiverRecord::Base
  belongs_to :user
end

resulting in:

SELECT "status_changes".* FROM "status_changes" WHERE "status_changes"."user_id" = 1 ORDER BY "status_changes"."created_at" DESC

Benefits:

  • you are strictly bound to Modelclass name => renaming table in model will not break the sql code (of if it will, it will explicitly break the syntax on Ruby level, not DB level)

  • you still have the benefit of explicitly saying what table.column the order should be

  • easier to re-factor parts to Query Objects

September 9, 2015
1 thank

Warning: prevents persistence but doesn't prevent setting

For example:

class Widget < ActiveRecord::Base
  attr_readonly :key
end
w = Widget.create! key: 'foo'
w.update! key: 'bar'
w.key #=> 'bar'
w.reload.key #=> 'foo'
September 8, 2015
1 thank

Favicon generator

Hello, I suggest you to try this favicon generator and creator, http://onlinefavicon.com/ , you can create favicon using drawing tool or add picture jpg or other file and make 16x16 or 32x32 ICO file, also see the gallery with favicons from other users or download the same, at end you can read description how to set up favicon to your site!

August 25, 2015
0 thanks

Using Arel

You can also use Arel.

For example:

class ArticlePage < ActiveRecord::Base
  belongs_to :article
  scope :published, -> { where.not(published_at: nil) }
  scope :all_ready, -> { select("every(workflow_state = 'ready') AS is_ready") }
end

class Article < ActiveRecord::Base
  has_many :article_pages
  def all_ready?
    ActiveRecord::Base.select_values(article_pages.all_ready,published) = 't'
  end
end
August 2, 2015
0 thanks

Skip validation

update_all : skip validations, and will save the object to the database regardless of its validity. They should be used with caution.

July 16, 2015
0 thanks

I would just use a validation instead of (the probably removed) :required

Just make sure you validate the presence of the association and not the foreign key, otherwise it will not work on new records.

The down side is that it will require the record in the cache, and will make a query otherwise. You can add `unless: :<foreign_key>?` If that’s a problem for you.

July 16, 2015
1 thank

Is :required still valid ?

I get this error when using :required => true

ArgumentError: Unknown key: :required. Valid keys are: :class_name, :class, :foreign_key, :validate, :autosave, :remote, :dependent, :primary_key, :inverse_of, :foreign_type, :polymorphic, :touch, :counter_cache

Is :required not a valid key anymore ?

July 6, 2015
0 thanks

For supported arguments, see see match

As of July, 2015, the v4.2.1 doc says “see match[rdoc-ref:Base#match]” without a URL. I think you want this one: http://apidock.com/rails/ActionDispatch/Routing/Mapper/Base/match

July 2, 2015
0 thanks

Usage with enum

With enum fields you must use integer values:

code

Model.update_all(type: Model.types[specific_type])