scala 匹配模式中的@_Scala中的模式匹配

淩亂°似流年 2023-03-05 09:55 90阅读 0赞

scala 匹配模式中的@

## Scala模式匹配 **(**Scala Pattern Matching**)** ##

**Scala pattern matching** is a commonly used feature which has huge support by Scala language. **Pattern matching in Scala** is the same as the switch in Java or another programming language.

**Scala模式匹配**是一种常用的功能，Scala语言对此功能具有巨大的支持。 **Scala**中的**模式匹配**与Java或其他编程语言中的开关相同。

Matching a pattern contains a sequence of alternative of the pattern to be considered. Each sequence is a case of the Scala pattern matching. For all alternatives, the case has expressions which are evaluated for matching pattern matches. The arrow symbol **'=>'** is used as a separator between the patterns and expressions.

匹配模式包含要考虑的模式的替代序列。 每个序列都是Scala模式匹配的情况。 对于所有替代方案，案例都有针对匹配模式匹配进行评估的表达式。 箭头符号**“ =>”**用作模式和表达式之间的分隔符。

The **match keyword** is used to define a pattern matching block. This block contain cases that are that turns that if matched will execute a set of expressions (a block of code).

**match关键字**用于定义模式匹配块。 该块包含的情况使得如果匹配将执行一组表达式(代码块)。

In Pattern matching, there must be at least one case (also called alternative) with sum values for which the input pattern can be matched. If no keyword is matched then the last **catch-all(\_)** case is executed. The expression that is evaluated after the matches found is actually a block code that is needed to be Evaluated. For a pattern-matching function, any sort of data can be matched based on first match policy (for you cases matching, the first one is used).

在模式匹配中，必须至少有一种情况(也称为替代)，其总和值可以匹配输入模式。 如果没有匹配的关键字，则执行最后一个**catch-all(\_)**情况。 找到匹配项后评估的表达式实际上是需要评估的块代码。 对于模式匹配功能，可以根据第一个匹配策略对任何类型的数据进行匹配(对于您所匹配的情况，将使用第一个)。

**Example:**

**例：**

object Demo {
        
        
        def matchno(x: Int): String = x match {
        
            case 1 => "Hello"
            case 2 => "Welcome"
            case _ => "to Scala "
        }
        
        def main(args: Array[String]) {
        
            println(matchno(3))
        }  
    }

**Output**

**输出量**

to Scala

**Code Explanation:**

**代码说明：**

The above code will print to Scala because number 3 is matched to the default value of the match pattern function. the function three values, matching cases 1,2 and default(\_).

上面的代码将打印到Scala，因为数字3与匹配模式函数的默认值匹配。 函数三个值，匹配情况1,2和default(\_)。

> 翻译自: [https://www.includehelp.com/scala/pattern-matching-in-scala.aspx][https_www.includehelp.com_scala_pattern-matching-in-scala.aspx]

scala 匹配模式中的@

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