CODEWITHSUNDEEP
xcodeswiftcore-data
Deproblemify
Deproblemify

Reputation: 3430

Swift: Check if variable is nil

I am currently learning Swift and I am experimenting with Core Data where I would like to save a linked list. To add an element at the end of the list I have a while-loop like this:

var curr = start
while (curr.nextElem != nil) {
    curr = curr.nextElem
}

The problem is though that curr.next != nil seems to be invalid, following error is shown: 'ListElem' is not convertible to UInt8

I noticed this error a few times before but always found a way around comparing but how can this be done in this case?

Upvotes: 0

Views: 303

Answers (1)

rickster
rickster

Reputation: 126167

Your ListElem.nextElem property seems to be returning an actual ListElem, so it can never be nil. For it to be able to be nil, it has to be of optional type (ListElem?).

Also, try the Xcode 6.3 beta — most of the error messages where Swift 1.1 said "I dunno what you're doing, so I'll just say you can't convert it to UInt8" have been replaced with better diagnostics in Swift 1.2.

Upvotes: 1

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