ruby - 我的 Ruby 条件是什么？

Question

以下条件语法在不使用 puts

的情况下在 irb 中显示字符串 'is true'

irb(main):001:0> if true
irb(main):002:1>   'is true'
irb(main):003:1> else
irb(main):004:1*   'is false'
irb(main):005:1> end
=> "is true"

...然而，当我在脚本中调用相同的语法并从命令行运行它时，它会被忽略。为什么？

# Odd behaviour:
puts "Why do only two of the three conditionals print?"

# This doesn't put anything to screen:
if true
  'is true_1'
else
  'is false'
end

puts "Seriously, why? Or better yet: how?"

# But this does:
if true
  puts 'is true_2'
else
  puts 'is false'
end

# And this works without "puts":
def truthiness
  if 1.send(:==, 1)
    'is true_3'
  else
    'is false'
  end
end

puts truthiness
puts "Weird."

当我将其作为脚本运行时，它显示:

"Why do only two of the three conditionals print?
Seriously, why? Or better yet: how?
is true_2
is true_3
Weird."

FWIW，我正在关注 Sandi Metz 的演讲“Nothing is Something” https://youtu.be/zc9OvLzS9mU......听这个: https://youtu.be/AULOC--qUOI抱歉，我是 Ruby 的新手，并试图了解它是如何做的。
编辑:有用资源:
http://ruby-doc.org/core-2.3.1/Kernel.html#method-i-puts
https://softwareengineering.stackexchange.com/questions/150824/is-the-puts-function-of-ruby-a-method-of-an-object

Answer 1

这里的 IRB 输出显示的是操作的返回值，这不一定是执行期间打印到 STDOUT(即终端)的内容。

您的脚本只是丢弃了返回值，您必须这样做:

val = if true
        'is true_1'
      else
        'is false'
      end

puts val