How to skip an index in a for loop in Swift

Question

I'm trying to skip in a random condition that if true, will skip a loop, but results are printing all elements 0,1,2,3,4 I know in Java if index is incremented index will skip, but this is not happening Swift.?

Update: this is a simplified version of some program I wrote, the print() has to be happen right after each loop, and index is ONLY incremented in some unknown conditions, I want it to behave like JAVA.

for var index in 0..<5 {
  print(index)//this prints 0,1,2,3,4, this must happen right after for loop
  if some unknown condition {
      index+=1
  }
}

You can use 'continue' with if clause like if index == 2 then continue!! — Ketan Parmar
– Ketan Parmar, Commented Jan 9, 2017 at 9:55
I don't understand what you want to do, because you want to check if an unknown condition is true... What do you want? A random number generator which will return which index should be removed?? Please be more clear. — Mr. Xcoder
– Mr. Xcoder, Commented Jan 9, 2017 at 9:57
I have a similar problem. My "unknown" condition is found inside the for-loop to determine whether the next iteration is skipped or not. I turned out declare a new variable to do the job — dondonhk
– dondonhk, Commented Dec 6, 2017 at 0:55
the second method I used is by while-loop, instead of for-loop. In that way the index is incremented as you want — dondonhk
– dondonhk, Commented Dec 6, 2017 at 1:18

vadian · Accepted Answer · 2017-01-09 09:02:27Z

48

The index is automatically incremented in the loop, you can skip an index with a where clause:

for index in 0..<5 where index != 2 {
    print(index)
}

answered Jan 9, 2017 at 9:02

vadian

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4 Comments

Sandeep Bhandari Over a year ago

@vandian : best answer among all :) Hence up vote :)

miracle-doh Over a year ago

what if $0 != 2 is not a known condition?

dfrib Over a year ago

@miracle-doh simply replace index != 2 with the condition you'd like to test (eg. for index in 0..<5 where myCondition(index) { ... })

Garrett Over a year ago

what if you're looping through objects that dont have a compareable interface I just need to skip the first index of my list. In something like java I could just start the loop at for(int i = 1 ... instead of i = 0

Sarabjit Singh · Accepted Answer · 2017-01-09 09:16:47Z

36

Please try this one:

for var index in 0..<5 {

  if index == 2 {
     continue
  }
  print(index)//this prints 0,1,3,4
}

edited Jan 9, 2017 at 9:16

answered Jan 9, 2017 at 9:04

Sarabjit Singh

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2 Comments

Mr. Xcoder Over a year ago

maybe without "2"(in the comment)

Sarabjit Singh Over a year ago

@ItsMeDom ... Thanks a lot

miracle-doh · Accepted Answer · 2017-01-09 09:47:11Z

5

This works. Not sure if it is the best way to do this.

var skip = false
for var index in 0..<5 {
  if (skip) {
    skip = false
    continue
  }

  print(index)
  if index == 2 {
      skip = true
  }
}

answered Jan 9, 2017 at 9:47

miracle-doh

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Comments

Mr. Xcoder · Accepted Answer · 2017-01-09 09:01:25Z

1

In your for-loop:

for var index in 0..<5 {
if index != 2{
   print(index)
}
}

answered Jan 9, 2017 at 9:01

Mr. Xcoder

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Comments

Sandeep Bhandari · Accepted Answer · 2017-01-09 09:00:33Z

0

for var index in 0..<5 {

  if index == 2 {
      //dont do anything
  }
  else {
     print(index)
  }
}

Isn't it that simple ??

answered Jan 9, 2017 at 9:00

Sandeep Bhandari

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1 Comment

Just a coder Over a year ago

well, if your upperlimit is 100million, it would be nice to simply skip to the number

Sri · Accepted Answer · 2017-01-09 09:35:57Z

0

(0..<5).filter({$0 != 2}).forEach{ x in print(x)}

(or) when the condition is unknown,

(0..<5).filter(isNumber2).forEach{ x in print (x)}

Note: isNumber2 is an external function that returns the boolean after evaluating the condition on the number. Your implementation of this function could be different.

var isNumber2: (Int) -> (Bool) = { return $0 != 2}

edited Jan 9, 2017 at 9:35

answered Jan 9, 2017 at 9:10

Sri

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1 Comment

miracle-doh Over a year ago

what if $0 != 2 is not a known condition?

Sneha · Accepted Answer · 2017-01-09 09:47:22Z

0

for index in 0 ..< 5 where (give your condition here) { print(index) }

If the condition is to skip index 3, for index in 0 ..< 5 where index != 3 { print(index) }

answered Jan 9, 2017 at 9:47

Sneha

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1 Comment

Sneha Over a year ago

@miracle-doh i dont think the boolean variable is needed to perform something simple as this

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