Question

我不明白为什么我的If else语句不能正常工作，如果我输入'y'那么它会评估if else语句的最后一部分。

puts('give 1: ')
nr1= Integer(gets)
puts('give 2: ')
nr2= Integer(gets)

selection = gets.to_s

if (selection == "y".upcase)
  puts "Result is #{nr1+nr2}"
elsif (selection =="v".upcase)
  puts "Result is #{nr1-nr2}"
else (selection == "k".upcase)
  puts "Result is #{nr1*nr2}"
end

Answer 1

进入的一个好习惯是将其分解为正确的case声明：

case (selection.upcase)
when 'Y'
  puts "Result is #{nr1+nr2}"
when 'V'
  puts "Result is #{nr1-nr2}"
when 'K'
  puts "Result is #{nr1*nr2}"
else
  puts "I don't know what you mean."
end

现在重要的是要注意selection == "y".upcase将selection与"Y"进行比较，它不会取消您的选择。我已经通过使用selection作为case正在操作的东西来调整{{1}}上的不区分大小写的匹配。

Answer 2

您缺少#chomp方法。由于\n附加到STDIN，您可以使用#chomp删除。

2.2.2 :032 > selection = gets
y
 => "y\n"
2.2.2 :033 > selection.chomp
 => "y"

您可以按如下方式更新代码：

selection = gets.to_s.chomp.upcase

if selection == 'Y'
  puts "Result is #{nr1+nr2}"
elsif selection == 'V'
  puts "Result is #{nr1-nr2}"
elsif selection == 'K'
  puts "Result is #{nr1*nr2}"
else
  puts 'Invalid input'
end

虽然，ruby case在这里最适合。类似的东西：

case selection.upcase
when 'Y'
  puts "Result is #{nr1 + nr2}"
when 'V'
  puts "Result is #{nr1 - nr2}"
when 'K'
  puts "Result is #{nr1 * nr2}"
else
  puts "Invalid input. Please provide a valid input [Y/V/K]"
end

Answer 3

一种选择是使用哈希。

h = { 'Y'=>:+, 'V'=>:-, 'K'=>:* }
selection = gets.chomp.upcase
puts "Result is #{nr1.public_send(h[selection], nr2)}" if h.key?(selection)

Ruby If Else语法评估

3 个答案: