Equatable == function implemented but still crashes

Question

In my app, I have a class Video which implements the Equatable protocol because I need to use the ==(lhs:,rhs:) -> Bool function. My class was as this :

class Video: Equatable {
    var url: URL!
    // Some other vars
}

func ==(lhs: Video, rhs: Video) -> Bool {
    return lhs.url == rhs.url
}

It always worked for me but some users had crashes with the reason protocol witness for static Equatable.== infix(A, A) -> Bool in conformance Video.

So I tried another way to implement this function which is

class Video {
    var url: URL!
    // Some other vars
}

extension Video: Equatable {
    static func ==(lhs: Video, rhs: Video) -> Bool {
        return lhs.url == rhs.url
    }
}

But the crashes still occur for some users and I don't understand why... Does someone already had this issue or know how to solve it?

`!` is your problem. – user28434'mstep Dec 07 '16 at 08:53 — user28434'mstep, Dec 07 '16 at 08:53

vadian · Accepted Answer · 2016-12-07T09:52:24.443

2

Since your url can be nil you have to consider this case in the implementation of ==

func ==(lhs: Video, rhs: Video) -> Bool {
    guard let lURL = lhs.url, let rURL = rhs.url else { return false }
    return lURL == rURL
}

If your design treats two objects with both nil urls as equal you have to add this case, too.

edited Dec 07 '16 at 09:52

answered Dec 07 '16 at 09:28

vadian

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1

If both URLs are `nil`, you should probably return `true`. – ganzogo Dec 07 '16 at 09:36
1

@ganzogo It depends on the needs, maybe `nil` values are irrelevant. Anyway the code avoids the crash. – vadian Dec 07 '16 at 09:48

score 0 · Answer 2 · answered Dec 07 '16 at 09:48

0

Indeed, I didn't think about the case the url is nil... My Video class also has an asset so if the url is nil, I return the comparison between the two assets. Thanks

answered Dec 07 '16 at 09:48

Thibaut Brnl

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5

Equatable == function implemented but still crashes

2 Answers2