Array count minus array count

Question

How can I show array count minus array count? I have two arrays like this:

var likedBy = [NSArray]()
var dislikedBy = [NSArray]()

And I am trying to get the count as a string on UITextLabel like this:

imageCell.likeLabel.text = self.likedBy.count - self.dislikedBy.count

But I get error:

No "-" candidates produce the expected contextual result type "String?"

Any suggestions?

Suggestion #1: *Read* the error message. – Suggestion #2: If you get compiler errors that you don't understand, *split* the expression into multiple statements: `let diff = self.likedBy.count - self.dislikedBy.count; imageCell.likeLabel.text = diff`. You should see the problem now! — Martin R, Apr 12 '16 at 08:40

Said Sikira · Answer 1 · 2016-04-12T08:40:48.180

3

You should use string interpolation with \() because count property returns Int and you need a String to set the text property:

imageCell.likeLabel.text = "\(self.likedBy.count - self.dislikedBy.count)"

edited Apr 12 '16 at 08:40

answered Apr 12 '16 at 08:35

Said Sikira

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Thanks! Quick question - In the `cellForItemAtIndexPath` - what is difference between indexPath.row and indexPath.item? – Roduck Nickes Apr 12 '16 at 08:40
`item`: An index number identifying an item in a section of a collection view. – André Slotta Apr 12 '16 at 08:42
Browse through http://stackoverflow.com/a/14765781/2035845 for more info on indexpath.item vs indexpath.row!! – Rashmi Ranjan mallick Apr 12 '16 at 08:43

score 2 · Answer 2 · edited Apr 12 '16 at 08:39

2

replace your line

imageCell.likeLabel.text = "\(self.likedBy.count - self.dislikedBy.count)"

edited Apr 12 '16 at 08:39

itsji10dra

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answered Apr 12 '16 at 08:39

Ankit Kushwah

539
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score 1 · Answer 3 · answered Apr 12 '16 at 08:51

You might also want to write an extension on NSArray to provide a element count difference so your code is cleaner and the responsibilities lie in the right place. As in, your main code flow is not interested in working out the difference between two array counts, it wants to know how many likes there are left, after the dislikes have been subtracted.

extension NSArray {
    func elementCountDiff(array: NSArray) -> Int {
        return self.count - array.count
    }
}

...

imageCell.likeLabel.text = String(self.likedBy.elementCountDiff(self.dislikedBy))

Array count minus array count

3 Answers3