ruby-on-rails - Ruby 表达式求值 : whitespace matters?

Question

假设现在是 1 月 19 日。如果您今天看这个问题，这并不难。

Date.today
 => Thu, 19 Jan 2012    # as expected

Date.today + 1
 => Fri, 20 Jan 2012    # as expected

Date.today+1
 => Fri, 20 Jan 2012    # as expected

Date.today +1
 => Thu, 19 Jan 2012    # ?!

我在这里错过了什么？

Answer 1

区别在于:

Date.today + 1 

是两个数值相加

Date.today +1 

是对方法 today 的调用，参数 sg(日历改革日)值为 +1

检查这一点的最佳方法是猴子修补包含调试输出的原始方法。以这个脚本为例:

require 'date'

class Date

  def self.today(sg=ITALY)
     puts "ITALY default("+sg.to_s+")" if sg==ITALY
     puts sg unless sg==ITALY
     jd = civil_to_jd(*(Time.now.to_a[3..5].reverse << sg))
     new0(jd_to_ajd(jd, 0, 0), 0, sg)
  end

end

puts "- Addition:"
Date.today + 1
puts "- Parameter:"
Date.today +1

这将打印以下控制台输出:

- Addition:
ITALY default(2299161)
- Parameter:
1