Notes

In this example

Post.find_by_sql ["SELECT title FROM posts WHERE author = ? AND created > ?", author_id, start_date]

The array is a parameter, so a space is required before the opening [, which is equivalent to write like this

Post.find_by_sql(["SELECT title FROM posts WHERE aut...

You can chain find_or_create_by with :where, or any custom scope.

E.g.:

User.where(girls: true).find_or_create_by(first_name: 'Scarlett')

scope :celebrities, -> { where(celebrity: true) }

User.celebrities.create_with(last_name: 'Johansson').find_or_create_by(first_name: 'Scarlett')

It's incorrect to state that belongs_to "Specifies a one-to-one association with another class".

If the inverse association is has_one then the model specifying belongs_to is the LHS of a zero/one-to-one relationship.

If the inverse association is has_many then the model specifying belongs_to is t...

perient view ==== Code example <%= render 'time_select', locals: { select_name: 'from_tiem'}%>

render view ==== Code example <%= locals[:select_name] %> not: ==== Code example <%= local_assigns[:select_name] %>

Reading source one can find detailed patterns: https://github.com/ruby/ruby/blob/ruby_1_9_3/lib/uri/common.rb

To also give dimension, is about 4.5 times faster then map {}.flatten.

It seems like this method was supported in versions prior to 4.0.2.

UPDATE never mind, wish I could delete this comment..

==== Another way to convert an array of arrays to a hash using inject:

array = [['A', 'a'], ['B', 'b'], ['C', 'c']]

hash = array.inject({}) do |memo, values|
memo.merge!(values.first => values.last)
end

hash
# => {'A' => 'a', 'B' => 'b', 'C' => 'c'}

This doesn't write files, at least not anymore. Since at least rails 4 Rack::Cache isn't included by default. In any case this method only ever set headers on the response.

This is terrible documentation. It makes it very hard to understand what the arguments mean.

The signature is

alias_method(p1, p2)

So what do p1 and p2 mean? The description doesn't refer to them at all, but to new_name and old_name. How are we supposed to know which is which?

And then it...

To prevent the "\
" character added at the end of each file pass in the "row_sep: nil" option:

[ "some", "array" ].to_csv                 # => "some, array\

"

[ "some", "array" ].to_csv( row_sep: nil ) # => "some, array"

By default link_to opens url as absolute if path does not contain http:// or https:// For Ex.

= link_to 'View', "test123.abc.com/ag/acf", target: :_blank, title: "Click to open url in a new tab"

Then it'll open the link with absolute path not only with test123.abc.com/ag/acf.

If link_to path cont...

You can add an index now directly on the foreign_key :

t.references(:user, index: true)

Fetching RSS feeds in the request/response cycle inside a Rails application is probably not the very best approach, as it will make your application as slow as the server serving RSS feeds. Another option is to do it asynchronously using a worker or a queue, but this can also become quite complex...

It still exists but you give it a block instead of creating a method:

==== <=2.3.8

def before_create
  self.login = self.first_name
end

==== Now

before_create :set_login

def set_login
  self.login = self.first_name
end

It’s intended that method returns an integer and if that integer is above zero, then the checkbox is checked. - more exactly, that's how it's determined whether value will be checked or not:

(@checked_value is checked_value, value is what object_name.method returns)

    def checked?(valu...

"Acceptable exception types maye be given as optional arguments. If the last argument is a String, it will be used as the error message."

"Acceptable exception types may be given as optional arguments. If the last argument is a String, it will be used as the error message."

Maybe this information will save you some time: parent associations (i.e. associations with foreign id in current record) are copied. Don't assume you'll get a safely editable object.

When the condition is true, the block is not rendered:

<%= link_to_if true, users_path, {}, {} do %>
<i class='fa fa-star'></i>
<% end %>

renders:

<a href="/users">/users</a>

But if the condition is false, the block will render:

<%= link_to_if false, users_path, {}, {} do...

Here, the class will be ignored:

<%= link_to_if false, 'Home', root_path, class: 'link' %> 
#=> Home