Active Support Improvements in Rails 5
Improvements in Date, Time and Datetime
参考这个PR，DHH 认为代码的可读性优先级高于DRY。所以增加了一堆 alias 方法。
prev_day and next_day
没啥说的，就是给 Date, Time 和 DateTime 的 #yesterday 和 #tomorrow 增加了另外一个名称。
same_time
Rails 4.x 的时候 next_week 和 prev_week 返回那个星期的开头时间。
Time.current #=> Fri, 12 Feb 2016 08:53:31 UTC +00:00
Time.current.next_week #=> Mon, 15 Feb 2016 00:00:00 UTC +00:00
Time.current.next_week(:tuesday) #=> Tue, 16 Feb 2016 00:00:00 UTC +00:00
Time.current.prev_week(:tuesday) #=> Tue, 02 Feb 2016 00:00:00 UTC +00:00
现在利用 same_time: true 我们可以拿到上周三了。
Time.current #=> Fri, 12 Feb 2016 09:15:10 UTC +00:00
Time.current.next_week #=> Mon, 15 Feb 2016 00:00:00 UTC +00:00
Time.current.next_week(same_time: true) #=> Mon, 15 Feb 2016 09:15:20 UTC +00:00
Time.current.prev_week #=> Mon, 01 Feb 2016 00:00:00 UTC +00:00
Time.current.prev_week(same_time: true) #=> Mon, 01 Feb 2016 09:16:50 UTC +00:00
on_weekend?
顾名思义，当周六、日的时候返回 true
Time.current #=> Fri, 12 Feb 2016 09:47:40 UTC +00:00
Time.current.on_weekend? #=> false
Time.current.tomorrow #=> Sat, 13 Feb 2016 09:48:47 UTC +00:00
Time.current.tomorrow.on_weekend? #=> true
on_weekday?
与 on_weekend? 相反。工作日的时候返回 true
next_weekday and prev_weekday
周五的时候 next_weekday 返回下周一
Time.days_in_year
# Gives number of days in current year, if year is not passed.
Time.days_in_year #=> 366
# Gives number of days in specified year, if year is passed.
Time.days_in_year(2015) #=> 365
Improvements in Enumerable
pluck
参考这个PR，现在只要是 Enumerable 对象都可以使用 pluck 方法了。
users = [{id: 1, name: 'Max'}, {id: 2, name: 'Mark'}, {id: 3, name: 'George'}]
users.pluck(:name) #=> ["Max", "Mark", "George"]
# Takes multiple arguments as well
users.pluck(:id, :name) #=> [[1, "Max"], [2, "Mark"], [3, "George"]]
这对性能上的改进显而易见。当 ActiveRecord 的 relation 已经加载完毕，再次执行 pluck 动作的话，会直接调用 Enumerable 的 pluck 方法，而不会再次生成 SQL 查询。
# With Rails 4.x
users = User.all
SELECT `users`.* FROM `users`
users.pluck(:id, :name)
SELECT "users"."id", "users"."name" FROM "users"
=> [[2, "Max"], [3, "Mark"], [4, "George"]]
# With Rails 5
users = User.all
SELECT "users".* FROM "users"
# does not fire any query
users.pluck(:id, :name)
=> [[1, "Max"], [2, "Mark"], [3, "George"]]
without
没错，又是一个语法糖，有兴趣的话直接看这个PR。
vehicles = ['Car', 'Bike', 'Truck', 'Bus']
vehicles.without("Car", "Bike") #=> ["Truck", "Bus"]
vehicles = {car: 'Hyundai', bike: 'Honda', bus: 'Mercedes', truck: 'Tata'}
vehicles.without(:bike, :bus) #=> {:car=>"Hyundai", :truck=>"Tata"}
Array#second_to_last and Array#third_to_last
从后往前查找元素。
['a', 'b', 'c', 'd', 'e'].second_to_last #=> "d"
['a', 'b', 'c', 'd', 'e'].third_to_last #=> "c"
Integer#positive? and Integer#negative?
判断一个数是正还是负，该方法 Ruby 2.3 以及内建。
4.positive? #=> true
4.negative? #=> false
-4.0.positive? #=> false
-4.0.negative? #=> true
Array#inquiry
PR，这是一个值得注意的特性。
利用 ArrayInquirer 将一个数组包裹起来，然后提供一些语法糖来查找其中的字符串内容。
利用 Array#inquiry 可以容易的创建 ArrayInquirer 对象。
users = [:mark, :max, :david]
array_inquirer1 = ActiveSupport::ArrayInquirer.new(users)
# creates ArrayInquirer object which is same as array_inquirer1 above
array_inquirer2 = users.inquiry
array_inquirer2.class #=> ActiveSupport::ArrayInquirer
# provides methods like:
array_inquirer2.mark? #=> true
array_inquirer2.john? #=> false
array_inquirer2.any?(:john, :mark) #=> true
array_inquirer2.any?(:mark, :david) #=> true
array_inquirer2.any?(:john, :louis) #=> false
