How to write multiple conditions in Kotlin for loop

user_2356570 0
Viewed 3092

This is the following code I have

val idNumber: String = "1342342"
var randomNumber = 0

for (number in idNumber) {
    if (randomNumber < 20) {
        // Do something
        randomNumber++
    }
}

Here I've a for loop which iterates through the idNumber and at the same time I've to check if randomNumber is less than 20.

In Java, I can write this as

for (int i = 0 ; i < idNumber.length() && randomNumber < 20 ; i++) {

}

How do I do the same in Kotlin?

I went through Stackoverflow for this problem and found this solution which explains to use a more functional approach. Please suggest me a good solution for the problem I mentioned above.

Edit 1: I understand that while loop can be used to do a logical and, but I would like to know what's the functional way of solving this.

Edit 2: Added answer, but still would love to hear from someone who can give a better insight to this problem

kotlin loops
2 Answers

It seems that in this case, randomNumber is really just a counter. If that is the case you can do this without having to maintain the state of randomNumber by using take():

idNumber.take(20).forEach { number ->
    ...
}

What this does is iterate over each Char in the idNumber string, but only at most 20 of them. If you were turning these into something else, you might want to consider map instead of forEach, which only has a side-effect and doesn't return anything.

Todd_497460

The solution is simple

idNumber.takeWhile { randomNumber < 20 }.forEach { number ->

}

As @pixix4 pointed out in the comment, the above solution doesn't work for non sequences, and so any change to randomNumber will not get reflected to the takeWhile block, since takeWhile block is executed first and afterwards forEach block is executed.

Adding asSequence() fixes the issue I reckon. The solution provided by @Todd is what I'm looking for ideally.

user_23565700
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