Cannot subscript a value of type '[String : Int]' with an index of type 'String?'

Question

I have the following code. When it runs, it triggers the error : Cannot subscript a value of type '[String : Int]' with an index of type 'String?'

Can someone please help

self.books = self.books.filter { $0.completed[MUser.sharedInstance.getUserId()] ?? 0 > 0 }

completed is declared as

var completed = [String : Int]()

getUserId() is obviously an optional. The error says the key must be non-optional. Basically it's the same issue as in your previous question. — vadian
– vadian, Commented Feb 13, 2020 at 17:32
@LouisaScheinost What do you mean, "copy" an array? They are already passed by value. — George
– George, Commented Feb 13, 2020 at 17:40

Robin Schmidt · Accepted Answer · 2020-02-13 17:40:35Z

1

The error indicates, that MUser.sharedInstance.getUserId() returns an optional.
You need to unwrap this:

self.books = self.books.filter {  
  guard let userID = MUser.sharedInstance.getUserId() else { return false }
  return $0.completed[userID] ?? 0 > 0 
}

answered Feb 13, 2020 at 17:40

Robin Schmidt

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