Kotlin 开发 - 双冒号操作符（引用顶层函数、引用成员函数、引用构造函数、引用属性、引用类）

双冒号操作符

1、引用顶层函数

• 直接引用::【函数名】

funisOdd(x:Int)=x%2!=0valnumbers=listOf(1,2,3)valoddNumbers=numbers.filter(::isOdd)println(oddNumbers)

// 等价于funisOdd(x:Int)=x%2!=0valnumbers=listOf(1,2,3)valoddNumbers=numbers.filter{isOdd(it)}println(oddNumbers)

2、引用成员函数

1. 未绑定引用【类名】::【成员函数】

vallist=listOf("a","bb","ccc")vallengths=list.map(String::length)println(lengths)

// 等价于vallist=listOf("a","bb","ccc")vallengths=list.map{it.length}println(lengths)

dataclassPerson(valname:String,valage:Int)vallist=listOf(Person("Alice",25),Person("Bob",30))valnames=list.map(Person::name)println(names)

// 等价于dataclassPerson(valname:String,valage:Int)vallist=listOf(Person("Alice",25),Person("Bob",30))valnames=list.map{it.name}println(names)

2. 已绑定引用【对象实例】::【成员函数】

dataclassPerson(valname:String,valage:Int)valp=Person("Alice",25)valnameGetter=p::nameprintln(nameGetter())

3、引用构造函数

dataclassPerson(valname:String,valage:Int)valcreatePerson=::Personvalp=createPerson("Alice",25)println(p)

4、引用属性

varcount=0funmain(){valcountProperty=::countprintln(countProperty.get())countProperty.set(5)println(count)}

• 对于局部变量，Kotlin 编译器不支持生成可修改的属性引用，只能生成只读的引用

funmain(){varcount=0valcountProperty=::countprintln(countProperty.get())countProperty.set(5)println(count)}

# 输出结果 Unresolved reference 'set'.

5、引用类

dataclassPerson(valname:String,valage:Int)valkClass:KClass<Person>=Person::classprintln(kClass.simpleName)