問題描述
如果評估的最後一個語句是 If 語句，Ruby 會返回什麼 (What is Returned in Ruby if the Last Statement Evaluated is an If Statement)
My understanding is that ruby returns the last statement evaluated in a function. What if the function ends with an if statement that evaluates to false
def thing(input)
item = input == "hi"
if item
[]
end
end
puts thing("hi").class #> Array
puts thing("not hi").class #> NilClass
I like this functionality (returning nil if the statement is false), but why isn't false returned (from the assignment to item)?
‑‑‑‑‑
參考解法
方法 1:
If your if statement doesn't result in any code being run, it returns nil, Otherwise, it returns the value of the code that was run. Irb is a good tool to experiment with such stuff.
irb(main):001:0> i = if false then end
=> nil
irb(main):002:0> i = if true then end
=> nil
irb(main):007:0> i = if false then "a" end
=> nil
irb(main):008:0> i = if false then "a" else "b" end
=> "b"
方法 2:
The return value is the value of the if expression is the value of the clause that was evaluated and not of the condition. In case no clause was evaluated (if without else), nil is returned:
irb(main):001:0> x = if false
irb(main):002:1> []
irb(main):003:1> end
=> nil
irb(main):004:0> x
=> nil
irb(main):005:0>
(by Tyler DeWitt、theglauber、davidrac)