case语句的变量绑定(p @ T)
假设以下场景：你需要从对象中提取值，但你又想将一个变量赋给该对象的整体。该怎么做呢？
我们来对前文中匹配Person 类的属性的实例做以下修改。
1 case class Address(street: String, city: String, country: String) 2 case class Person(name: String, age: Int, address: Address) 3 4 val alice = Person("Alice", 25, Address("1 Scala Lane", "Chicago", "USA")) 5 val bob = Person("Bob", 29, Address("2 Java Ave.", "Miami", "USA")) 6 val charlie = Person("Charlie", 32, Address("3 Python Ct.", "Boston", "USA")) 7 8 for (person <- Seq(alice, bob, charlie)) { 9 person match { 10 case p@Person("Alice", 25, address) => println(s"Hi Alice! $p") 11 case p@Person("Bob", 29, a@Address(street, city, country)) => 12 println(s"Hi ${p.name}! age ${p.age}, in ${a.city}") 13 case p@Person(name, age, _) => 14 println(s"Who are you, $age year-old person named $name? $p") 15 } 16 } 17 }
p @ …的语法将整个 Person 类的实例赋值给了变量 p，类似地，a @ …也将整个 Address实例赋值给了变量。以下为修改版本的实例输出。（为适应排版做了格式化。）
记住，如果不需要从Person 实例中提取属性值，我们只要写为p: Person => …就可以了。
