ROR tricks

Few tricks

Some of the ror syntax that I was not using in my regular life.

  • Hash[…]
Hash[1,2,3,4,5,6]
#=> {1=>2, 3=>4, 5=>6}
  • Double star(**)
def new_method(a, *b, **c)
  return a, b, c
end

a is a regular parameter. *b will take all the parameters passed after the first one and put them in an array. **c will take any parameter given in the format key: value at the end of the method call.

new_method(1)
#=> [1, [], {}]

new_method(1, 2, 3)
#=> [1, [2, 3]]

new_method(1, 2, 3, a: 4, b: 5)
#=> [1, [2, 3], {a: 4, b: 5}]
  • Mandatory hash parameters
def new_method(a:, b:, c: 'hello')
  return a, b, c
end

new_method(a: 1, b: 2)
#=> [1, 2, 'hello']

new_method(a: 1, b: 2, c: 3)
#=> [1, 2, 3]

This was introduced in Ruby 2.0. We can define the keys in the parameters.

  • Default value for hash
a = Hash.new(0)
a[:a]
# => 0

a = Hash.new({})
a[:a]
# => {}

a = Hash.new('hello')
a[:a]
# => "hello"

By default, when trying to access a value not defined in a hash, we will receive nil. We can actually change this at initialization.

  • The ‘presence’ method: [@object.presence]
hash = {a: 1, b: 2}

hash[a].present?
#=> true

hash[a].presence
#=> 1

hash[c].present?
#=> nil

hash[c].presence
#=> nil

The presence method goes one step further than @object.present? by returning the attribute or value being checked for rather than just true.

  • Helper methods
helper.display_name('first name', 'last name')

Rails view helpers can be accessed in the rails console.

  • Sanbox mode
rails c --sandbox

When rails console is under the sandbox option, all the database operations are rolled back in the end when the console is closed. All the queries run under a transaction which is rolled back in the end. Hence there is no chance of changing the actual data by mistake while accessing the databases through the rails console.

  • Access last evaluated result
User.last
a = _.id
#=> 14

Last evaluated expression in the console can be accessed through the (_).

  • Query by range
User.where(created_at: 10.days.ago..Time.now).to_sql

It applies the “BETWEEN” in the sql query prepared by the active record.

  • Pretend generate
rails g model comment body:text post_id:integer -p
invoke  active_record
create    db/migrate/20141002023923_create_comments.rb
create    app/models/comment.rb
invoke    test_unit
create      test/models/comment_test.rb
create      test/fixtures/comments.yml

If you need to find out what files will be created/modified, you can run a pretend migration.

  • rake notes
# TODO
# FIXME
# OPTIMIZE

We can do a search for the string within your project to see all these comments. Alternatively, Rails provide rake notes, which will show the list of the comments that begins with these strings:

$  rake notes
app/controllers/application_controller.rb:
  * [6] [FIXME] Title is not dynamic for each page

app/controllers/posts_controller.rb:
  * [7] [TODO] It is better if we can avoid these unecessary joins.

app/models/post.rb:
  * [3] [OPTIMIZE] This is too slow. Better to use pluck
  • rake restart

It restarts the rails server. It just touches the [tmp/restart.txt] file.

 rake restart

Thanks for reading!!!

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