54 lines
1.2 KiB
Markdown
54 lines
1.2 KiB
Markdown
---
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title: Ruby Conditionals
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localeTitle: Ruby条件
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---
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Ruby有几个常用的条件。
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## 如果声明
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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。
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* ```ruby
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fruit = :apple
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if fruit == :apple
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puts "Your fruit is an apple"
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elsif fruit == :orange
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puts "Your fruit is an orange"
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else
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puts "This is not an apple or an orange"
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end
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```
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### 除非声明
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除非语句与if语句相反。它与否定的if语句相同。
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* `ruby happy = true if !happy puts "This person is not happy" end` 以上陈述等同于以下陈述
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* `ruby unless happy puts "This person is not happy" end`
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## 三元声明
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三元语句用作短条件语句。它写成如下
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* `ruby game = "won" fans = game == "won" ? "happy" : unhappy fans # => "happy"`
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## 案例陈述
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case语句类似于if / elsif / else语句
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* ```ruby
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fruit = :apple
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case fruit
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when :apple
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puts "Your fruit is an apple"
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when :orange
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puts "Your fruit is an orange"
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else
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puts "This is not an apple or an orange"
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end
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``` |