ios - Optional binding with try? and as? still produces an optional type

Question

I have code for executing an NSFetchRequest and casting its result to an array of my custom data model type. Fetching may throw but I don't want to care about the error so I use try?, and I also use as? in casting. In Swift 2, this used to be just fine, but Swift 3 produces a double optional:

var expenses: [Expense]? {
    let request = NSFetchRequest<NSFetchRequestResult>(entityName: Expense.entityName)
    request.predicate = NSPredicate(format: "dateSpent >= %@ AND dateSpent <= %@", [self.startDate, self.endDate])

    // Returns [Expense]? because right side is [Expense]??
    if let expenses = try? App.mainQueueContext.fetch(request) as? [Expense],
        expenses?.isEmpty == false {
        return expenses
    }
    return nil
}

How can I rephrase the right side of my optional binding in if let so that its type will simply be an array [Expense]? I think it looks absurd that in the following boolean condition (which used to be a where clause), the array is still optional.

Answer 1

You must wrap your try? call within parenthesis like this?:

if let expenses = (try? App.mainQueueContext.fetch(request)) as? [Expense]

That's because as? has a higher precedence than try? (probably because try? can be applied to the whole expression).