1.xx.()->xx 这啥玩意啊

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        test { "" }
        test { hello() }
        test { zeze() }
        test { zeze("what fuck~") }
    }
    fun test(block: MainActivity.() -> String) {
        println(block)
    }
}
fun MainActivity.hello(): String {
    return "what fuck";
}

fun MainActivity.zeze(): String {
    return "你好吗";
}

fun MainActivity.zeze(hell: String? = null): String {
    return "你好吗$hell";
}