One of my co-workers just noticed a problem with the (bridged) API of our
Objective-C framework, when used from Swift 3 (but not earlier). We have a
class CBLQueryRow that includes the following:
@property (readonly) id key;
- (nullable id) keyAtIndex: (NSUInteger)index;
In Swift this becomes
open var key: Any { get }
open func key(at index: UInt) -> Any?
The problem is that any reference to `key` now seems to refer to a pointer to
the method, not to the property, leading to compiler diagnostics like the
following (where `row` is a CBLQueryRow):
TaskListsViewController.swift:95:40: warning: cast from '(UInt) -> Any?' to
unrelated type 'String' always fails
cell.textLabel?.text = row.key as? String
~~~~~~~ ^ ~~~~~~
That’s a warning not an error, but obviously at runtime the `as?` would always
fail and result in nil.
This is rather bad for us, since the `key` property is a crucial part of the
API, while the `key()` method that pre-empts it is obscure and little-used.
I can reproduce this in a playground in Xcode 8 like so:
protocol QueryRow {
var key: Any { get }
func key(at index: UInt) -> Any?
}
var row: QueryRow
row.key as? String
In addition to the valid error about `row` being uninitialized, I also get the
cast failure.
What’s the best workaround for this?
—Jens_______________________________________________
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