Question

我设置了一个rails API，我希望每隔3天（72小时）从一个数组中pop。我有点迷失了如何迭代日期以正确选择我的数组。这就是我目前正在使用的内容。

def index
  theme = ["Superhero", "Star-Wars", "Pokemon", "Other-Animals", "Hats", "Sports"]
  current_theme = theme.shuffle.pop
  start_time = DateTime.new(2017,5,9,00,00)
  end_time = DateTime.new(2018,5,9,00,00)

  start_time.upto(end_time) do |t|
    cycle = t*3
    while t = cycle do 
      render json: current_theme
      // bad loop 
    end
  end
end

Answer 1

您可以使用Enumerator

中的.cycle，.step和.next全部

require 'date'
start_time = DateTime.new(2017,5,9,00,00)
end_time = DateTime.new(2018,5,9,00,00)

# create an enumerator
theme = ["Superhero", "Star-Wars", "Pokemon", "Other-Animals", "Hats", "Sports"].cycle

# iterate using step over 3 days
start_time.step(end_time, 3) do |date|
    puts "#{date} - #{theme.next}"
    # Do something like this:
    render json: theme if DateTime.now.beginning_of_day <= date + 2
end
# => 2017-05-09T00:00:00+00:00 - Superhero
# => 2017-05-12T00:00:00+00:00 - Star-Wars
# => 2017-05-15T00:00:00+00:00 - Pokemon
# => 2017-05-18T00:00:00+00:00 - Other-Animals
# => 2017-05-21T00:00:00+00:00 - Hats
# => 2017-05-24T00:00:00+00:00 - Sports
# => 2017-05-27T00:00:00+00:00 - Superhero
#...

同样DateTime.now.beginning_of_day取决于ActiveSupport，但您可以轻松实现类似的内容，Date.today.to_datetime等

Answer 2

使用std::tuple进行此类操作。 whenever是一个伟大的宝石，可以使用Ruby DSL创建和更新cronjob。例如，您可以将任务编写为：

crontab

每3天从一个数组拉出..时间迭代

2 个答案: