Crash on property/distinct query

[pfvernon2]

Xcode 11.4.1, Swift 5.x, iOS 13.4.1

I'm seeing a general protection fault when attempting a property/distinct query. This is occurring both on hardware and in the simulator.

I've replicated this crash in the following trivial example.

class ExampleEntity: Entity {
    var id: Id = 0

    // objectbox: index
    var test: String = ""
}

func test() {
    do {
        //Boilerplate… create store and open box
        let databaseName = "notes"
        let appSupport = try FileManager.default.url(for: .applicationSupportDirectory,
                                                     in: .userDomainMask,
                                                     appropriateFor: nil,
                                                     create: true)
            .appendingPathComponent(Bundle.main.bundleIdentifier!)
        let directory = appSupport.appendingPathComponent(databaseName)
        try FileManager.default.createDirectory(at: directory,
                                                withIntermediateDirectories: true,
                                                attributes: nil)
        let store = try Store(directoryPath: directory.path)
        let exampleEntityBox = store.box(for: ExampleEntity.self)

        //if box is empty add some random values
        var boxCount = try exampleEntityBox.count()
        if boxCount == 0 {
            let testCases = ["foo", "bar", "foobar", "barfoo"];
            for _ in 1...100 {
                let exampleEntity = ExampleEntity()
                exampleEntity.test = testCases.randomElement() ?? "default"
                try exampleEntityBox.put(exampleEntity)
            }
            boxCount = try exampleEntityBox.count()
        }

        assert(boxCount > 0)

        //get distinct values the hard way
        let all = try exampleEntityBox.all()
        let testSet = Set(all.map { $0.test })
        print(testSet)

        //MARK: Crash - general protection fault
        //get distinct values the objectbox way
        let distinct: [String] = try exampleEntityBox.query().build()
            .property(ExampleEntity.test)
            .distinct(caseSensitiveCompare: false)
            .findStrings()

        print(distinct)

    } catch {
        print("error")
    }
}

Am I doing something incorrectly? Is this a known issue?

[greenrobot]

A "general protection fault" should never happen, looking into it...

[greenrobot]

Reproduced! Thank you for the example code! 👍

If you follow the example of the property query Swift docs and assign the query to a variable, it should work.

If you put everything in one line, the main query gets discarded and thus crashes. Will check now if we can prevent this.

[greenrobot]

Improved internally, will be part of next release (1.3).

[pfvernon2]

Thank for you looking into the issue and working on a fix!

I have confirmed that creating the query as a variable before executing the property/distinct lookup works as expected:

//Does NOT crash!
let query = try exampleEntityBox.query().build()
let distinct: [String] = try query.property(ExampleEntity.test).distinct(caseSensitiveCompare: false).findStrings()
print(distinct)

I could not find an example of a property/distinct query in your documentation that was structured in this way, however. The one example I could find was expressed as a single line as I did above. I mention this only because you may want to update your documentation until a fix can be released.

From the ObjectBox Swift documentation:

[greenrobot]

Thanks for pointing to those docs... 🤔

If you know how, you could try this out now using https://github.com/objectbox/objectbox-swift-spec-staging/releases/tag/v1.3.x.

If not, the official release comes soon.

[pfvernon2]

Looks good! No more crash using the single line form in my trivial example project.

Thanks again for the quick fix.

[greenrobot]

1.3.0 has been released with a fix.