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[SR-9036] Passing a dictionary as parameter of initializer of ObjC class in Swift, yields "null" value #51539

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swift-ci opened this issue Oct 18, 2018 · 3 comments

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@swift-ci
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@swift-ci swift-ci commented Oct 18, 2018

Previous ID SR-9036
Radar rdar://problem/45962521
Original Reporter petar.belokonski (JIRA User)
Type Bug

Attachment: Download

Environment

SwiftObjCPlay.zip

Additional Detail from JIRA
Votes 0
Component/s
Labels Bug, 4.2Regression
Assignee None
Priority Medium

md5: 05dc781faf00fc6c7a8030c7994f7a76

Issue Description:

Weird situation I've stumbled upon once upgrading to XCode 10.

I have an ObjectiveC class which I initialize in Swift. The initializer accepts NSDictionary as a parameter. If I pass in the dictionary directly into the initializer like so:

let car = Car(parts: [myKey : myValue])

Then, back in ObjC world, when printing the contents of the dictionary it shows the value as "(null)".

Everything works fine if I do:

let parts = [myKey : myValue]
let car = Car(parts: parts)

This issue exists on any version of Swift on XCode 10. The issue doesn't exist on XCode 9.

I am attaching a sample project where this is illustrated.

@belkadan
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@belkadan belkadan commented Oct 31, 2018

Reproduced. Very strange; what Petar didn't mention was that when the dictionary is bridged back to Swift, the value is there.

@swift-ci create

@belkadan
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@belkadan belkadan commented Oct 31, 2018

The difference between the two invocations is whether we create a [String?: String] dictionary and convert it to [AnyHashable: Any], or whether we just start with [AnyHashable: Any] from the beginning. But they should indeed have the same observable behavior.

@lorentey
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@lorentey lorentey commented Nov 12, 2018

This is because Optional doesn't currently have a custom AnyHashable representation, making it incompatible with its wrapped values when converted to AnyHashable.

Adding such a representation is tracked in https://bugs.swift.org/browse/SR-9047, following the forum discussion at https://forums.swift.org/t/xcode-10-swift-objc-dictionary-compatibility/17148.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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