30.seconds.ago是如何实现的？

Question

我在这里发现了这个问题.

并且真的很想知道30.seconds.ago在Rails中实现类似内容的技术解释.

方法链？Numeric使用方法:http: //api.rubyonrails.org/classes/Numeric.html#method-i-seconds.

还有什么？

Answer 1

这是执行seconds:

  def seconds
    ActiveSupport::Duration.new(self, [[:seconds, self]])
  end

而且,这里是执行ago:

# Calculates a new Time or Date that is as far in the past
# as this Duration represents.
def ago(time = ::Time.current)
  sum(-1, time)
end

而且,这里是在以下sum方法中使用的方法的实现ago:

  def sum(sign, time = ::Time.current) #:nodoc:
    parts.inject(time) do |t,(type,number)|
      if t.acts_like?(:time) || t.acts_like?(:date)
        if type == :seconds
          t.since(sign * number)
        else
          t.advance(type => sign * number)
        end
      else
        raise ::ArgumentError, "expected a time or date, got #{time.inspect}"
      end
    end
  end

要完全理解它,您应该按照方法调用并在Rails源代码中查找它们的实现,就像我刚才给您看到的那样.

在Rails代码库中查找方法定义的一种简单方法是source_location在Rails控制台中使用:

> 30.method(:seconds).source_location
# => ["/Users/rislam/.rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/core_ext/numeric/time.rb", 19]
> 30.seconds.method(:ago).source_location
# => ["/Users/rislam/.rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/duration.rb", 108]