For-In Loops multiple conditions

Question

With the new update to Xcode 7.3, a lot of issues appeared related with the new version of Swift 3. One of them says "C-style for statement is deprecated and will be removed in a future version of Swift" (this appears in traditional for statements).

One of this loops has more than one condition:

for i = 0; i < 5 && i < products.count; i += 1 {

}

My question is, is there any elegant way (not use break) to include this double condition in a for-in loop of Swift:

for i in 0 ..< 5 {

}

Queenhood

Answer 1

It would be just as you're saying if you described it out loud:

for i in 0 ..< min(5, products.count) { ... }

That said, I suspect you really mean:

for product in products.prefix(5) { ... }

which is less error-prone than anything that requires subscripting.

It's possible you actually need an integer index (though this is rare), in which case you mean:

for (index, product) in products.enumerate().prefix(5) { ... }

Or you could even get a real index if you wanted with:

for (index, product) in zip(products.indices, products).prefix(5) { ... }

Shamblin

Your answer demonstrates perfectly why Apple is removing the C-style for statement: because there are other, way more Swifty ways to accomplish the same thing, and often people only use the old style for statement to iterate an array anyway. – Situated

Very complete answer! Thanks! with the two first was enough for me. About the two last answer (which both have compile errors): in the third answer, enumerate is a method and in the fourth answer "Value of type Range<DctionaryIndex<String, String>> has no member zip", so this method seems that doesn't exist for this type. Thanks you very much! – Queenhood

Fixed the syntax. Thanks for noting it. – Shamblin

Answer 2

You can use && operator with where condition like

let arr = [1,2,3,4,5,6,7,8,9]

for i in 1...arr.count where i < 5  {
    print(i)
}
//output:- 1 2 3 4

for i in 1...100 where i > 40 && i < 50 && (i % 2 == 0) {
     print(i)
}
//output:- 42 44 46 48

Mcnalley

Is it possible to add optional binding after the where? – Soccer

@Soccer I don't think so we can use let statement here, however, we can use != nil here or If you are trying to check class type then you can use is as well like object is UIButton – Mcnalley

Answer 3

Another way to do so would be like this

for i in 0 ..< 5 where i < products.count {
}

Dorina

Answer 4

One more example. Loop through all UILabel in subviews:

for label in view.subviews where label is UILabel {
    print(label.text)
}

UPDATE

Now the subview inside the loop is UIView and needs to additionally case it to UILabel

for subview in view.subviews where subview is UILabel {
    let label = subview as? UILabel
    print("\(label?.text ?? "")")
}

Vitrics

In the current implementation of Swift this doesn't work, because label isn't cast to UILabel, even though it is known to be a UILabel. It would be a good feature but it isn't implemented yet. – Wearproof

@Wearproof thank you to point it out! I've updated my answer. – Vitrics

Answer 5

Here’s a simple solution:

var x = 0
while (x < foo.length && x < bar.length) {

  // Loop body goes here

  x += 1
}

Dade