For loop based on array length in Swift

Question

I have been trying to take the length of an array and use that length to set the amount of times that my loop should execute. This is my code:

  if notes.count != names.count {
        notes.removeAllObjects()
        var nameArrayLength = names.count
        for index in nameArrayLength {
            notes.insertObject("", atIndex: (index-1))
        }
    }

At the moment I just get the error:

Int does not have a member named 'Generator'

Seems like a fairly simple issue, but I haven't yet figured out a solution. Any ideas?

You are trying to insert an object in an empty NSMutableArray, in this case you should use .addObject — Leo Dabus
– Leo Dabus, Commented Nov 2, 2014 at 1:05
If index is already occupied, the objects at index and beyond are shifted by adding 1 to their indices to make room. — Leo Dabus
– Leo Dabus, Commented Nov 2, 2014 at 1:06
Note that NSArray objects are not like C arrays. That is, even though you specify a size when you create an array, the specified size is regarded as a “hint”; the actual size of the array is still 0. This means that you cannot insert an object at an index greater than the current count of an array. For example, if an array contains two objects, its size is 2, so you can add objects at indices 0, 1, or 2. Index 3 is illegal and out of bounds; if you try to add an object at index 3 (when the size of the array is 2), NSMutableArray raises an exception. — Leo Dabus
– Leo Dabus, Commented Nov 2, 2014 at 1:06

vacawama · Accepted Answer · 2014-11-02 00:32:47Z

39

You need to specify the range. If you want to include nameArrayLength:

for index in 1...nameArrayLength {
}

If you want to stop 1 before nameArrayLength:

for index in 1..<nameArrayLength {
}

answered Nov 2, 2014 at 0:32

vacawama

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1 Comment

vacawama Over a year ago

@HoldOffHunger, I started at 1 so that the OP's notes.insertObject("", atIndex: (index-1)) wouldn't crash.

Ketan Patel · Accepted Answer · 2020-08-04 10:25:56Z

18

for i in 0..< names.count {
    //YOUR LOGIC....
}

for name in 0..< names.count {
    //YOUR LOGIC....
    print(name)
}

for (index, name) in names.enumerated()
{
    //YOUR LOGIC....
    print(name)
    print(index)//0, 1, 2, 3 ...
}

edited Aug 4, 2020 at 10:25

answered Mar 1, 2017 at 12:08

Ketan Patel

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2 Comments

thevikasnayak Over a year ago

Just awesome. Working as expected.

Gopal Kohli Over a year ago

it should be for i in 0..<names.count {. "check for space after <"

meaning-matters · Accepted Answer · 2018-02-19 20:45:45Z

4

In Swift 3 and Swift 4 you can do:

for (index, name) in names.enumerated()
{
     ...
}

edited Feb 19, 2018 at 20:45

answered Mar 1, 2017 at 11:42

meaning-matters

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2 Comments

meaning-matters Over a year ago

@MicheleDall'Agata I'm also from the C era. Great to have you back as a programmer!

Michele Dall'Agata Over a year ago

Ah, just doing some Swift self training. The beginning has been atrocious! :-D Especially with those damn escaping closures..

Paul.s · Accepted Answer · 2018-02-19 20:59:07Z

1

You can loop over the Array's indices

for index in names.indices {
    ...
}

If you are just wanting to fill an array with empty strings you could do

notes = Array(repeating: "", count: names.count)

answered Feb 19, 2018 at 20:59

Paul.s

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