Question

具有一个实现通用类型为“ This”类的接口的类

是否有一种无需强制转换的方法？

简单代码：

interface Triggerable<This: Triggerable<This>> {
    var trigger: (This) -> Unit
    fun triggerNow() = trigger(this as This)
}
class Test : Triggerable<Test>{
    override var trigger: (Test) -> Unit = { /*...*/ }
}

有点复杂：

interface TriggerInterface<T> {
    val trigger: (T) -> Unit
    fun triggerNow()
}
interface Triggerable<T: Triggerable<T>>: TriggerInterface<T> {
    override fun triggerNow() = trigger(this as T)
}
interface Signalable<T>: TriggerInterface<T> {
    var value: T
    override fun triggerNow() = trigger(value)
}
class Test : Triggerable<Test>{
    override val trigger: (Test) -> Unit = { /*...*/ }
}

Answer 1

应该可能是这样

from pyspark.sql.window import Window
from pyspark.sql import functions as F
from pyspark.sql.functions import when
w= Window().partitionBy("I_id","p_id").orderBy(F.col("xyz").asc_nulls_first())
w2= Window().partitionBy("I_id","p_id")
df.withColumn("xyz1",F.count(F.col("xyz").isNotNull()).over(w))\
.withColumn("xyz2", F.max(F.row_number().over(w)).over(w2))\
.withColumn("xyz3", F.first("xyz1").over(w))\
.withColumn("xyz10", F.col("xyz2")-F.col("xyz3"))\
.withColumn("xyz9", F.when((F.col("xyz2")-F.col("xyz3"))%2!=0, F.col("xyz2")-F.col("xyz3")+1).otherwise(F.col("xyz2")-F.col("xyz3")))\
.withColumn("xyz4", (F.col("xyz9")/2))\
.withColumn("xyz6", F.col("xyz4")+F.col("xyz3"))\
.withColumn("xyz7", F.when(F.col("xyz10")%2==0,(F.col("xyz4")+F.col("xyz3")+1)).otherwise(F.lit(None)))\
.withColumn("xyz5", F.row_number().over(w))\
.withColumn("medianr", F.when(F.col("xyz6")==F.col("xyz5"), F.col("xyz")).when(F.col("xyz7")==F.col("xyz5"),F.col("xyz")).otherwise(F.lit(None)))\
.withColumn("medianr2", (F.mean("medianr").over(w2)))\
.withColumn("xyz", F.when(F.col("xyz").isNull(), F.col("medianr2")).otherwise(F.col("xyz")))\
.select("I_id","p_id","xyz")\
.orderBy("I_id").show()

+----+----+---+
|I_id|p_id|xyz|
+----+----+---+
|   1|   5|  4|
|   1|   5|  1|
|   1|   5|  4|
|   1|   5|  4|
|   2|   5|  2|
|   2|   5|  2|
|   2|   5|  1|
|   2|   5|  2|
|   2|   5|  4|
+----+----+---+

选中http://www.angelikalanger.com/GenericsFAQ/FAQSections/ProgrammingIdioms.html#FAQ206

我个人也建议重新考虑是否确实需要TriggerInterface和Triggerable（其中一个继承自另一个）。

Answer 2

调用override fun triggerNow() = trigger(this as T)就是要将Triggerable<T>强制转换为T，这就是编译器警告您有关未经检查的强制转换的原因

拥有

    val trigger: (TriggerInterface<T>) -> Unit

将允许您在不强制转换的情况下调用触发器

    override fun triggerNow() = trigger(this)

实际执行

override val trigger: (Test) -> Unit = { /*...*/ }

您需要Test的实例才能在尚未在代码中任何位置声明的触发器内传递

接口与实现接口的类的泛型类型有关？

2 个答案: