我可以省略我在 Kotlin 中不使用的接口方法吗

发布于11月18日

What if I am only interested in onSee and do not care for other events? Can I at least omit the methods that have no return values?

interface EventHandler
{
    fun onSee()
    fun onHear()
    fun onSmell()
    fun onTouch()
    fun onAwake()
    fun onSleep()
}

fun addEventHandler(handler:EventHandler)
{

}

fun Main()
{
    addEventHandler(object:EventHandler
    {
        override fun onSee()
        {
            print("I see.")
        }
    })
}

推荐答案

Sure you can only implement one interface method, all you have to do is to provide a default implementation for the other methods in the interface declaration

interface EventHandler {
    fun onSee()
    fun onHear() { /* default implementation */ }
    fun onSmell(){ /* default implementation */ }
    fun onTouch(){ /* default implementation */ }
    fun onAwake(){ /* default implementation */ }
    fun onSleep(){ /* default implementation */ }
}

Now when you create an instance of this interface you only need to provide a compulsory implementation for onSee() method, rest are optional

If you're not the author of the original interface

interface OnSeeEventHandler: EventHandler {
    override fun onHear() { /* default implementation */ }
    override fun onSmell(){ /* default implementation */ }
    override fun onTouch(){ /* default implementation */ }
    override fun onAwake(){ /* default implementation */ }
    override fun onSleep(){ /* default implementation */ }
}

并且使用OnSeeEventHandler只提供onSee个方法实现