Does Kotlin have an “enumerate” function like Pyth

问题:

In Python I can write:

for i, element in enumerate(my_list):
    print i          # the index, starting from 0
    print element    # the list-element

How can I write this in Kotlin?

回答1:

There is a forEachIndexed function in the standard library:

myList.forEachIndexed { i, element ->
    println(i)
    println(element)
}

See @s1m0nw1's answer as well, withIndex is also a really nice way to iterate through an Iterable.

回答2:

Iterations in Kotlin: Some Alternatives

1. Like already said, forEachIndexed is a good way to iterate.

2. Alternative 1: the extension withIndex, defined for Iterable types, can be used in for-each:

   val ints = arrayListOf(1, 2, 3, 4, 5)
   
   for ((i, e) in ints.withIndex()) {
       println("$i: $e")
   }
   

3. Alternative 2: extension property indices is available for Collection, Array etc., which let's you iterate like in a common for loop as known from C, Java etc:

   for(i in ints.indices){
        println("$i: ${ints[i]}")
   }