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May 31, 2019
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Make zh_cn/tour/pattern_matching.md up to date #1341

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10 changes: 5 additions & 5 deletions _zh-cn/tour/pattern-matching.md
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Original file line number Diff line number Diff line change
Expand Up @@ -66,8 +66,8 @@ case class VoiceRecording(contactName: String, link: String) extends Notificatio
```
def showNotification(notification: Notification): String = {
notification match {
case Email(email, title, _) =>
s"You got an email from $email with title: $title"
case Email(sender, title, _) =>
s"You got an email from $sender with title: $title"
case SMS(number, message) =>
s"You got an SMS from $number! Message: $message"
case VoiceRecording(name, link) =>
Expand All @@ -81,15 +81,15 @@ println(showNotification(someSms)) // prints You got an SMS from 12345! Message

println(showNotification(someVoiceRecording)) // you received a Voice Recording from Tom! Click the link to hear it: voicerecording.org/id/123
```
`showNotification`函数接受一个抽象类`Notification`对象作为输入参数，然后匹配其具体类型。（也就是判断它是一个`Email`，`SMS`，还是`VoiceRecording`）。在`case Email(email, title, _)`中，对象的`email`和`title`属性在返回值中被使用，而`body`属性则被忽略，故使用`_`代替。
`showNotification`函数接受一个抽象类`Notification`对象作为输入参数，然后匹配其具体类型。（也就是判断它是一个`Email`，`SMS`，还是`VoiceRecording`）。在`case Email(sender, title, _)`中，对象的`sender`和`title`属性在返回值中被使用，而`body`属性则被忽略，故使用`_`代替。

## 模式守卫（Pattern gaurds）
为了让匹配更加具体，可以使用模式守卫，也就是在模式后面加上`if <boolean expression>`。
```

def showImportantNotification(notification: Notification, importantPeopleInfo: Seq[String]): String = {
notification match {
case Email(email, _, _) if importantPeopleInfo.contains(email) =>
case Email(sender, _, _) if importantPeopleInfo.contains(sender) =>
"You got an email from special someone!"
case SMS(number, _) if importantPeopleInfo.contains(number) =>
"You got an SMS from special someone!"
Expand All @@ -111,7 +111,7 @@ println(showImportantNotification(importantEmail, importantPeopleInfo))
println(showImportantNotification(importantSms, importantPeopleInfo))
```

在`case Email(email, _, _) if importantPeopleInfo.contains(email)`中，除了要求`notification`是`Email`类型外，还需要`email`在重要人物列表`importantPeopleInfo`中，才会匹配到该模式。
在`case Email(sender, _, _) if importantPeopleInfo.contains(sender)`中，除了要求`notification`是`Email`类型外，还需要`sender`在重要人物列表`importantPeopleInfo`中，才会匹配到该模式。


## 仅匹配类型
Expand Down