Scala萃取器

╰+哭是因爲堅強的太久メ 2023-03-05 07:29 6阅读 0赞

## Scala | 提取器 **(**Scala | Extractors**)** ##

An **extractor** is a special type of object that has some special methods. These methods are: **apply() and unapply()**.

**提取器**是一种特殊的对象，具有一些特殊的方法。 这些方法是： **apply()和unapply()** 。

*  The **apply() method** of extractor object is used to feeding values for the object, it takes parameter values, formats them and adds them to the object.
    
    提取器对象的**apply()方法**用于馈送对象的值，它获取参数值，对其进行格式化并将其添加到对象中。
 *  The **unapply() method** of extractor object is used to delete values from the object, it matches the value and removes them from the object list.
    
    提取器对象的**unapply()方法**用于从对象中删除值，它匹配该值并将其从对象列表中删除。

### 抽气机的工作 **(**Working of extractors**)** ###

Let's take an example of an object that **apply()** as well as **unapply()** method. The **apply()** method takes arguments and adds them to class. The **unapply()** does the exact opposite, it takes arguments, matches them and then deletes, i.e. deconstructs.

让我们举一个**apply()**对象以及**unapply()**方法的示例。 **apply()**方法接受参数并将其添加到类中。 **unapply()的**作用恰恰相反，它接受参数，将其匹配，然后删除，即解构。

**Program:**

**程序：**

object Student 
    {
         
    	def main(args: Array[String]) 
    	{
         
    		def apply(name: String, result: String) =
    		{
         
    			name +" is "+ result 
    		} 
    
    		def unapply(x: String): Option[(String, String)] =
    		{
         
    			val y = x.split("is") 
    			if (y.length == 2 && y(1)=="Pass") 
    			{
         
    				Some(y(0), y(1)) 
    			
    			} 
    			else
    					None
    		} 
    		println ("The Apply method returns : " + 
    						apply("Ram", "Pass")) 
    		println ("The Unapply method returns : " + 
    						unapply("RamisPass")) 
    	} 
    }

**Output**

**输出量**

The Apply method returns : Ram is Pass
    The Unapply method returns : Some((Ram,Pass))

**Explanation:**

**说明：**

The **unapply() method** here, checking if the student is passed and removes it based on the result.

这里的**unapply()方法**检查是否通过了学生并根据结果将其删除。

> 翻译自: [https://www.includehelp.com/scala/extractors.aspx][https_www.includehelp.com_scala_extractors.aspx]

[https_www.includehelp.com_scala_extractors.aspx]: https://www.includehelp.com/scala/extractors.aspx