接下来会讲解关于各种模式匹配，从中就会知道模式匹配的重要性
关于Type、Array、List、Tuple模式解析
1.Type模式匹配代码解析
//关于Type类型的模式匹配 //匹配 Int类型、string类型、Map类型[_,_]代表任意类型的k,v def match_type(t : Any) = t match { case p : Int => println("It is Integer") case p : String => println("It is String, the content is : " + p) case m: Map[_, _] => m.foreach(println) case _ => println("Unknown type!!!") } match_type(2) match_type("Spark") match_type(Map("Scala" -> "Spark"))
2.Array模式匹配代码解析
//关于Array模式匹配 def match_array(arr : Any) = arr match { //匹配数组数据第一个为0 case Array(0) => println("Array:" + "0") //匹配数组两个数字 case Array(x, y) => println("Array:" + x + " " +y) case Array(0, _*) => println("Array:" + "0 ...") case _ => println("something else") } match_array(Array(0)) match_array(Array(0,1)) match_array(Array(0,1,2,3,4,5))
3.List模式匹配代码解析
//匹配list类型数据 用：：来匹配
def match_list(lst : Any) = lst match {
case 0 :: Nil => println("List:" + "0")
case x :: y :: Nil => println("List:" + x + " " + y)
case 0 :: tail => println("List:" + "0 ...")
case _ => println("something else")
}
match_list(List(0))
match_list(List(3,4))
match_list(List(0,1,2,3,4,5))
4.Tuple，模式匹配代码解析
//tuple模式匹配 -->tuple模式是比较随意的 def match_tuple(tuple : Any) = tuple match { case (0, _) => println("Tuple:" + "0") case (x, 0) => println("Tuple:" + x ) case _ => println("something else") } match_tuple((0,"Scala")) match_tuple((2,0)) match_tuple((0,1,2,3,4,5))
关于Scala中提取器Extractor解析
1.Extractor实战解析
2.Extractor源码解析：提取器就好比apply函数一样，获取用户的
//提取器就是获取函数中参数 从中获取数据 -->数组的模式匹配就是提取器获取数据 def match_array(arr : Any) = arr match { case Array(0) => println("Array:" + "0") case Array(x, y) => println("Array:" + x + " " +y) case Array(0, _*) => println("Array:" + "0 ...") case _ => println("something else") } match_array(Array(0)) match_array(Array(0,1)) match_array(Array(0,1,2,3,4,5)) //正则式与模式匹配结合形成了一个函数就获取匹配出的数值与字符 val pattern = "([0-9]+) ([a-z]+)".r "20150628 hadoop" match { case pattern(num, item) => println(num + " : " + item) }
Case class和Case object代码解析
1.Case class代码解析：模式匹配中使用case class和case object中消息传递中用的比较多，能够根据业务进行消息的发送
2.Case object代码解析：可以理解为单例模式
object case_class_object { def main(args: Array[String]): Unit = { //定义一个模式匹配 def caseOps(person: Person) = person match { case Student(age) => println("I am " + age + "years old") case Worker(_, salary) => println("Wow, I got " + salary) case Shared => println("No property") } caseOps(Worker(1,19)) caseOps(Student(19)) caseOps(Shared) //因为继承时候会发现参数都是常量-->需要改变的时候可以复制对象进行改变 val worker = Worker(29, 10000.1) val worker2 = worker.copy(salary = 19.95) val worker3 = worker.copy(age = 30) } } //case class object在消息传输过程中起很重要地位 //抽象类 abstract class Person //继承抽象类 带有Int类型的常量 case class Student(age: Int) extends Person //继承抽象类 带有Int类型与double的常量 case class Worker(age: Int, salary: Double) extends Person //继承抽象类 --object case object Shared extends Person
模式匹配高级实战：嵌套的Case class
1.嵌套的Case class解析：在匹配模式中参数也使用case class和caseobject
2.Case object实战解析
def main(args: Array[String]): Unit = { //定义一个模式匹配 case class def caseclass_nested(person: Item) = person match { //匹配项中第一二个参数可以不计，第三课参数用art代替Book对象用@符号引用类似也这样 case Bundle(_, _, art @ Book(_, _), rest @ _*) => println(art.description + " : " + art.price) case Bundle(_, _, Book(descr, _), _*) => println("The first description is :" + descr) case _ => println("Oops!") } //调用定义的模式匹配 caseclass_nested(Bundle("1111 Special's", 30.0,Book("Scala for the Spark Developer", 69.95), Bundle("Hadoop", 40.0,Book("Hive", 79.95),Book("HBase", 32.95)))) caseclass_nested(Bundle("1212 Special's", 35.0, Book("Spark for the Impatient", 39.95))) } } abstract class Item case class Book(description: String, price: Double) extends Item //继承抽象类，并且参数中嵌套了抽象类 -->这就是类中嵌套类 case class Bundle(description: String, price: Double, items: Item*) extends Item
就讲这么多了，明天继续....
希望大家关注王家林老师的视频，本系列也是从他的视频中学习的，他是微信号(18610086859)
百度云地址:http://pan.baidu.com/s/1kTw4Idp