freeCodeCamp/guide/chinese/ruby/ruby-conditionals/index.md

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Ruby Conditionals	Ruby条件

Ruby有几个常用的条件。

如果声明

在许多编程语言中非常常见的条件，语句测试条件是否为真，然后分支到指定的操作。 if语句包含一个if ， 任何数量的elsif和至多一个else声明。

• fruit = :apple 
  
   if fruit == :apple 
    puts "Your fruit is an apple" 
   elsif fruit == :orange 
    puts "Your fruit is an orange" 
   else 
    puts "This is not an apple or an orange" 
   end 
  
  

除非声明

除非语句与if语句相反。它与否定的if语句相同。

• ruby happy = true if !happy puts "This person is not happy" end 以上陈述等同于以下陈述
• ruby unless happy puts "This person is not happy" end

句尾条件

在ruby当里我们也常将条件至于句尾

• puts "Your fruit is an apple" if fruit == :apple
• puts "This is not an apple" unless fruit == :apple

三元声明

三元语句用作短条件语句。它写成如下

• ruby game = "won" fans = game == "won" ? "happy" : unhappy fans # => "happy"

案例陈述

case语句类似于if / elsif / else语句

• fruit = :apple 
  
   case fruit 
   when :apple 
    puts "Your fruit is an apple" 
   when :orange 
    puts "Your fruit is an orange" 
   else 
    puts "This is not an apple or an orange" 
   end