“如果"和“如果"有什么区别?带有“then"的语句在最后? [英] What is the difference between "if" statements with "then" at the end?

问题描述

当我们在 if 语句的末尾放置一个 then 时，这两个 Ruby if 语句之间有什么区别?

What's the difference between these two Ruby if statements when we put a then at the end of the if statement?

if(val == "hi") then
  something.meth("hello")
else
  something.meth("right")
end

和

if(val == "hi")
  something.meth("hello")
else
  something.meth("right")
end

推荐答案

then 是一个分隔符，帮助 Ruby 识别条件和表达式的真实部分.

then is a delimiter to help Ruby identify the condition and the true-part of the expression.

if 条件 then true-part else false-part end

if condition then true-part else false-part end

then 是可选的除非您想在一行中编写一个 if 表达式.对于跨越多行的 if-else-end，换行符作为分隔符将条件与真实部分分开

then is optional unless you want to write an if expression in one line. For an if-else-end spanning multiple lines the newline acts as a delimiter to split the conditional from the true-part

# can't use newline as delimiter, need keywords
puts if (val == 1) then '1' else 'Not 1' end

# can use newline as delimiter
puts if (val == 1)
  '1'
else
  'Not 1'
end

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