Question

某些时候基于某些条件，它可能想要在for循环中跳过（或向前）几步，

怎么做才是kolin？

一个简化的用例：

val datArray  = arrayOf(1, 2, 3......)

/**
 * start from the index to process some data, return how many data has been 
   consumed
*/
fun processData_1(startIndex: Int) : Int  {
   // process dataArray starting from the index of startIndex
   // return the data it has processed
}
fun processData_2(startIndex: Int) : Int  {
   // process dataArray starting from the index of startIndex
   // return the data it has processed
}

在Java中，它可能是：

for (int i=0; i<datArray.lenght-1; i++) {
   int processed = processData_1(i);
   i += processed; // jump a few steps for those have been processed, then start 2nd process
   if (i<datArray.lenght-1) { 
       processed = processData_2(i);
       i += processed;
   }
}

如何在kotlin中做到这一点？

for(i in array.indices){
  val processed = processData(i);
  // todo
}

Answer 1

使用while：

var i = 0

while (i < datArray.length - 1) {
    var processed = processData_1(i)
    i += processed // jump a few steps for those have been processed, then start 2nd process
    if (i < datArray.length - 1) {
        processed = processData_2(i)
        i += processed
    }
    i++
}

Answer 2

您可以按照此处Kotlin文档中的说明continue执行此操作：https://kotlinlang.org/docs/reference/returns.html

示例：

val names = arrayOf("james", "john", "jim", "jacob", "johan")
for (name in names) {
    if(name.length <= 4) continue
    println(name)
}

这只会打印超过4个字符的名称（因为它会跳过长度为4及以下的名称）

编辑：这一次只跳过一次迭代。因此，如果要跳过多个，可以将进程状态存储在其他位置，并检查每次迭代的状态。

kotlin，如何动态改变for循环节奏

2 个答案: