A global h2 style probably isn’t going to last more than a month before everyone starts changing it inline...

...than it should, this expression requires 4 attempts to match the string: Attempt Group $1 Group $2 Expression result 1 "aaabbb" not matched not matched 2 "aaabb" not matched

...bbb)/ only requires a single attempt to match "aaabbb": "aaabbb" =~ /^(a+)(bbb)/ Attempt Group $1 Group $2 Expression result 1 "aaa" "bbb" matched! Because greedy quantifiers start backtracking when an...

...the method (and not out of the first block or something similar). def test [1, 2, 3].each do |counter| example { return counter } end return 'test' end test # => 1

...when we look at what was said above about the expected return value): # bad [1, 2, 3].each { |counter| break counter if counter.even? } # => 2 [1, 3].each { |counter| break counter...

In RubyMine you can use find and replace with capture groups (.*?) and backreferences $1 (if you have several groups: $[Capture-Group ID]). Named captures (? .*) are also supported. Examples

...expression captures whatever is contained by two double quotes. Fill in replace field with '$1'. The $1 references what was captured. RubyMine shows you a preview of the result, so...

...opening a form, JavaScript makes a request to acquire a lock for that record (1). After 20 seconds the JavaScript starts polling the server (2), to check if another user...

When the PC was low on resources (parallel_tests), acquiring the lock (1) took so long that the client starts polling for updates (2) before the initial lock...

@email = email @newsletter = newsletter end end User.new( 'Mr.', 'John', 'Doe', 'Potsdamer Platz 1', '10117', 'Berlin', '+49 0151 1122334455', 'john.doe@example.com', true ) Using keyword arguments Using keyword arguments is easier...

salutation: 'Mr.', first_name: 'John', last_name: 'Doe', street_and_number: 'Potsdamer Platz 1', zip_code: '10117', city: 'Berlin', phone_number: '+49 0151 1122334455', email: 'john.doe@example.com', newsletter: true )

...column_value(value) method in active record is traced (simplified output): git log -n 1 --pretty=oneline -G 'convert_number_column_value(value)' -- activerecord/lib/active_record/base.rb ceb33f84933639d3b61aac62e5e71fd087ab65ed Split out most of the...

...activerecord/lib/active_record/base.rb - def convert_number_column_value(value) - if value == false - 0 - elsif value == true - 1 - elsif value.is_a?(String) && value.blank? - nil - else - value - end - end activerecord/lib/active_record/attribute_methods/write.rb + def convert_number_column...

...options = Selenium::WebDriver::Chrome::Options.new options.add_argument('--disable-infobars') options.add_emulation(device_metrics: { width: 1280, height: 960, touch: false }) unless ENV.key?('NO_HEADLESS') options.add_argument('--headless') options.add_argument('--disable-gpu...

...app, browser: :chrome, options: options) end Selenium::WebDriver.logger.level = :error Headless Chrome in legacy Capybara 1 projects If you're working on a legacy project with Capybara version 1.x, the...

...database's EXPLAIN style. For example, it looks like this on MySQL: User.where(id: 1).includes(:articles).explain EXPLAIN for: SELECT `users`.* FROM `users`  WHERE `users`.`id` = 1 +----+-------------+-------+-------+---------------+

...type | table | type  | possible_keys | +----+-------------+-------+-------+---------------+ |  1 | SIMPLE      | users | const | PRIMARY       | +----+-------------+-------+-------+---------------+ +---------+---------+-------+------+-------+ | key     | key_len | ref   | rows | Extra | +---------+---------+-------+------+-------+ | PRIMARY | 4       | const |    1 |       | +---------+---------+-------+------+-------+   1 row in set (0.00 sec)   EXPLAIN for: SELECT `articles...

echo "> Deleting remote branch ..." git push origin --delete $merged_branch_name exit 1 else echo "x Did not delete the \"$merged_branch_name\" branch." fi

...the branch deleted: $ git merge ds/foo Updating 338e82e38..2d4269c81 Fast-forward foo | 0 1 file changed, 0 insertions(+), 0 deletions(-) create mode 100644 foo > You have just merged the...

...the copied invoice and the creation of its items. This list of changes (e.g. 12 INSERT statements) will be committed in a single atomic operation, or not at all. This...

...order, you might get a deadlock. For instance, transaction A wants to change row #1 and row #2. Transaction B wants to change the same rows, but in different order...

...NULL values with the + value. The sum value will be NULL. MySQL: mysql> select 1 + 2 + 3; +-----------+ | 1 + 2 + 3 | +-----------+ | 6 | +-----------+ 1 row in set (0,00 sec)

+--------------+ | 1 + NULL + 3 | +--------------+ | NULL | +--------------+ 1 row in set (0,00 sec) Postgres: test_database=# select 1 + 2 + 3; ?column? ---------- 6 (1 row) test_database=# select 1 + NULL...

...contained values. If your project uses Lodash or Underscore.js, you can use _.isEqual(): _.isEqual([1, 2], [2, 3]) // => false _.isEqual([1, 2], [1, 2]) // => true If your project already uses...

...Unpoly you may also use up.util.isEqual() in the same way: up.util.isEqual([1, 2], [2, 3]) // => false up.util.isEqual([1, 2], [1, 2]) // => true If you are writing server-side code in...

...foo@example.com'; +----+-------------+-------+-------+----------------------+----------------------+---------+-------+------+-------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+-------+----------------------+----------------------+---------+-------+------+-------+ | 1 | SIMPLE | users | const | index_users_on_email | index_users_on_email | 768 | const | 1 | | +----+-------------+-------+-------+----------------------+----------------------+---------+-------+------+-------+

...data types. Like integers for string fields: mysql> EXPLAIN SELECT * FROM users WHERE email = 12345; +----+-------------+-------+------+----------------------+------+---------+------+--------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+----------------------+------+---------+------+--------+-------------+

...You might think that the following queries yield the same result: User.where(movie_ids: [16, 17]) User.where(movie_ids: [17, 16]) Turn's out - they are not! They do care...

...the where_array_matches method below. Note that it does not care about duplicates - [1, 2, 2] is handled identically to [1, 2]: # lib/ext/active_record/relation.rb class ActiveRecord::Relation def where_array...

...OpenGraph image Some social networks display your image with an aspect ratio of 2:1 (wide), some with (1:1), some both. Facebook supports only 1.91:1. Images that do...

...make sure relevant content is still visible when cropped. We recommend a resolution of 1200x630. Note that Facebook does not support SVG images for og:image. You should use PNG...

...can globally disable animations like this: up.motion.config.enabled = false Disabling animations in AngularJS In AngularJS 1.x you can globally disable animations like this: angular.module('myApp', []).run(['$animate', function($animate) { $animate.enabled...

...AJAX, I've found it helpful to limit the number of concurrent requests to 1. This will implicit serialize UI interactions that make an AJAX request. You can configure Unpoly...

...for hash equality other.name == name end end bob = Person.new('bob') phone_list = { bob => '0821 123', } phone_list[bob] # returns '0821 123' phone_list[Person.new('bob')] # returns nil [bob, Person.new('bob...

[ [0] #<Person:0x0000559054263420 @name="bob">, [1] #<Person:0x000055905404ee50 @name="bob"> ] Only after implementing hash we get the expected results: class Person ... def hash name.hash end end bob = Person.new('bob...

2 application servers 6 Rails worker processes in each application server 1 background job server with Sidekiq (will spawn 10 threads by default) When your code does...

...you may use the following number of connections: (2 app servers * 6 app workers) + (1 job server * 10 sidekiq workers) = 12 + 10 = 22 connections When your code does use ActiveRecord...

...be using this example tree (from the acts_as_nested_set docs): root | +-- Child 1 | | | +-- Child 1.1 | | | +-- Child 1.2 | +-- Child 2 | +-- Child 2.1 | +-- Child 2.2 Option 1: Parent Association

This would serialize the example above to this table: id | parent_id | data ---+-----------+---------- 1 | NULL | root 2 | 1 | Child 1 3 | 2 | Child 1.1 4 | 2 | Child 1.2...

...Rails do the logic # Good User.where.not(id: []).to_sql => SELECT "users".* FROM "users" WHERE (1=1) User.where.not(id: [1]).to_sql => SELECT "users".* FROM "users" WHERE ("users"."id" != 1) User.where.not...

...id: [1, 2]).to_sql => SELECT "users".* FROM "users" WHERE "users"."id" NOT IN (1, 2) Rails < 4 Before Rails 4, you needed to work around this yourself: # Good excluded_ids.blank...

...Rails 5 does not halt callback chain if false is returned Legacy Rails versions (1-4) Goal Rails version Within before_* Within after_* Cancel later callbacks Rails 1-4

return false Rollback the transaction Rails 1-4 return false raise ActiveRecord::Rollback Take care that your callbacks don't accidentally return false, since that cancels the chain in...

...the net total is calculated from the gross total: gross = items.sum(&:total) vat = (gross * (1 - (1 / VAT_RATE))).round(2) net = gross - vat Don't show VAT amounts for individual...

end create_table :items do |t| t.integer :invoice_id t.decimal :unit_price, :precision => 10, :scale => 2 t.integer :quantity t.timestamps end Note how we are using a DECIMAL column rather...