Kotlin 类型别名

类型别名

1.类型别名为现有类型提供替代名称

2.类型别名不会引入新类型 它们等效于相应的底层类型

// 定义
typealias NodeSet = Set<Network.Node>

typealias FileTable<K> = MutableMap<K, MutableList<File>>

typealias MyHandler = (Int, String, Any) -> Unit

typealias Predicate<T> = (T) -> Boolean

// 内部类
class A {
    inner class Inner
}
class B {
    inner class Inner
}

typealias AInner = A.Inner
typealias BInner = B.Inner

// 
typealias Predicate<T> = (T) -> Boolean

fun foo(p: Predicate<Int>) = p(42)

fun main() {
    val f: (Int) -> Boolean = { it > 0 }
    println(foo(f)) // 输出 "true"

    val p: Predicate<Int> = { it > 0 }
    println(listOf(1, -2).filter(p)) // 输出 "[1]"
}