Working with implicit array values inside a closure

Question

I have a books array of struct Book that I am looping through trying to find if one of the book's properties is equal to a specific predefined value, and then I'd like to rearrange the element

if books.contains(where: { $0.structProperty == value }) {

    books.rearrange(from: $0, to: 1)
}

And this is the rearrange function declared in an array extension file

extension Array {
    mutating func rearrange(from: Int, to: Int) {
        insert(remove(at: from), at: to)
    }
}

With this setup I am getting this compile error:

Anonymous closure argument not contained in a closure

How can I go about achieving it without relying on a for loop?

Sulthan · Accepted Answer · 2018-05-20 14:54:39Z

1

contains(where:) returns a boolean indicating whether a matching element is present in the array or not, and

{
    books.rearrange(from: $0, to: 1)
}

is not a closure – it is a code block in the if-statement.

You need index(where:) which gives you the position of the first matching element (or nil if none is present):

if let idx = books.index(where: { $0.structProperty == value }) {
    books.rearrange(from: idx, to: 1)
}

Note also that the first index of an array is zero, so if your intention is to move the array element to the front then it should be

books.rearrange(from: idx, to: 0)

edited May 20, 2018 at 14:54

Sulthan

130k23 gold badges223 silver badges277 bronze badges

answered May 20, 2018 at 14:08

Martin R

541k98 gold badges1.3k silver badges1.4k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Tarek Over a year ago

Thanks that worked. The reason I had it to: 1 is because I actually wanted to rearrange it to appear 2nd in a UITableView.

Collectives™ on Stack Overflow

Working with implicit array values inside a closure

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related