1.lambda 表达式
package com.jmj.myapp.lamdbaimport javax.security.auth.callback.Callbackfun main() {1.test1 {println(this+1) }}fun <T> T.test1(callback:T.() -> Unit) {this.callback()
}
package com.jmj.myapp.lamdbaimport javax.security.auth.callback.Callbackfun main() {test(1) {println(this)}}fun <T> test(re: T, callback:T.() -> Unit) {re.callback()
}
2.通配符
package com.tiger.mykotlinapp.tongpeifufun main() {//*==Anyval list: List<*> = listOf("123", null, 1)list.forEach {println(it is Int)}}3.where关键字
package com.tiger.mykotlinapp.whereDemofun main() {MyClass<Prm>(Prm())test<Prm>()
}interface A
interface B
interface Cclass Prm:A,B,C
//这是 和 三个满足才算
class MyClass<T> (var num:T) where T:A,T:B,T:C {fun test(num: T){println("输出:$num")}
}fun <T>test() where T:A,T:B,T:C{}4.Out 和 In关键字
都是子类泛型变成父类
out是get方法，子类提升父类输出
in是set方法，子类提升父类输入
5.by委托
一般是委托接口和属性的
5.1 接口委托
package com.tiger.mykotlinapp.byfun main() {println(HomeService(HomeDaoImpl(),ADaoImpl()).getAllData())println(HomeService(HomeDaoImpl(),ADaoImpl()).getById(123))
}
interface HomeDao{fun getAllData():List<String>
}interface ADao{fun getById(id:Int):String
}class HomeDaoImpl:HomeDao{override fun getAllData(): List<String> {return listOf("home")}}class ADaoImpl:ADao{override fun getById(id:Int): String {return id.toString();}}
//将 HomeDaoImpl委托 给 HomeService by后面跟的是实现类的对象 这里只能委托接口，抽象类和普通类委托不了
class HomeService(homeDaoImpl: HomeDaoImpl,aDaoImpl: ADaoImpl):HomeDao by homeDaoImpl,ADao by aDaoImpl{fun getRedisData():String{return "redis";}
}5.2 属性委托
package com.tiger.mykotlinapp.byimport kotlin.properties.ReadWriteProperty
import kotlin.reflect.KPropertyfun main() {//将属性委托给类 顶层作用域委托var test:String by MyTestClass()test="213";println(test)
}//test并不属于哪个类 就用nothing
//第一个泛型 是委托属性所属的那个类，第二个泛型是委托属性的类型
class MyTestClass:ReadWriteProperty<Nothing?,String>{private var myVar="";override fun getValue(thisRef: Nothing?, property: KProperty<*>): String {return myVar}override fun setValue(thisRef: Nothing?, property: KProperty<*>, value: String) {this.myVar = value}}package com.tiger.mykotlinapp.byimport kotlin.properties.ReadWriteProperty
import kotlin.reflect.KPropertyfun main() {A().apply {atest="123";println(atest)}
// B().apply {
// atest="asda";
// println(atest)
// }
}class A{var atest:String by MyTestClass1()
}
//class B{
// var atest:String by MyTestClass1()
//}//test并不属于哪个类 就用nothing
//第一个泛型 是委托属性所属的那个类，第二个泛型是委托属性的类型
class MyTestClass1: ReadWriteProperty<A, String> {private var myVar = ""override fun getValue(thisRef: A, property: KProperty<*>): String {println("调用类委托的get")return myVar}override fun setValue(thisRef: A, property: KProperty<*>, value: String) {println("调用类委托的set")this.myVar= value}}
5.3 延迟委托
package com.tiger.mykotlinapp.byfun main() {
// //延迟委托
// //只能初始化一次。不能重复赋值，所以是val
// val test by lazy{
// println("初始化了Test")
// "hello"
// }
// //线程安全只会初始化一次
// println(test)
// println(test)val a = Ab()println(a.aTest)println(a.aTest)}class Ab{val aTest:Boolean by lazy {println("1")println("1")println("1")println("1")println("1")println("1")true}
}5.4 监听委托
package com.tiger.mykotlinapp.ObeserveWeiTuoimport kotlin.properties.Delegatesfun main() {var test by Delegates.observable("hello"){_,oldVal,newVal->//监听到test发生变化后调用的值println("oldval $oldVal")println("newVal $newVal")}test="tees"test="test"println(test)
}
