我的Ruby有什么条件？

Question

下面的条件语法显示irb中的字符串“是真”而不使用puts

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"

...yet当我在脚本中调用相同的语法并从命令行运行它时，它将被忽略。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."

当我将它作为脚本运行时，它会显示：

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

FWIW，我跟随着Sandi的演讲“什么都不是什么”https://youtu.be/zc9OvLzS9mU ...and在听这段话：https://youtu.be/AULOC--qUOI道歉，因为我对Ruby很陌生，并且试图思考它是如何做到的。

编辑:有用的资源：

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输出显示操作的返回值，这不一定是在执行过程中打印到STDOUT (即终端)的内容。

您的脚本正在丢弃返回值，您必须这样做：

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

puts val