Parse "unrecognized selector sent to instance" while accessing PFObject members

Question

I've got a weird issue with accessing member fields using dot notation. Example:

SettingsModel

class SettingsModel: PFObject, PFSubclassing {

    override class func initialize() {
        struct Static {
            static var onceToken : dispatch_once_t = 0;
        }
        dispatch_once(&Static.onceToken) {
            self.registerSubclass()
        }
    }

    static func parseClassName() -> String {
        return "Settings"
    }

    @NSManaged var name:String
    @NSManaged var code:String
    @NSManaged var friend:FriendsModel

}

FriendsModel

class FriendsModel: PFObject, PFSubclassing {

    override class func initialize() {
        struct Static {
            static var onceToken : dispatch_once_t = 0;
        }
        dispatch_once(&Static.onceToken) {
            self.registerSubclass()
        }
    }

    static func parseClassName() -> String {
        return "Friends"
    }

    @NSManaged var user:PFUser
    @NSManaged var settings:SettingsModel
}

When I try to access friends name using mySettings.friend.settings.name I'm getting unrecognized selector on "settings".

But interestingly enough when I use (mySettings.friend["settings"] as SettingsModel).name it works. I've intentionally omitted all the conditional unwrapping, etc. - I've got valid PFObject of the right type with all the data...

I'm sure it's something trivial but can't figure it out... Any help would be appreciated. Using Parse 1.8.2.

Answer 1

It looks like FriendsModel was not successfully registered as a Parse subclass, despite your implementation of PFSubclassing. It could be the case that the initialize() of FriendsModel is not yet called when you access it via mySettings.friend.settings.name.

To solve this issue you can register your FriendsModel subclass earlier with Parse by calling FriendsModel.registerSubclass(), just before the location where you call Parse.setApplicationId(..).

This is how I solved these kinds of issues myself, I hope it helps in your case too.

Answer 2

wow...I think I found the reason behind your problem, but it would be one of those "how in hell can this be the reason" type of solutions. I came across this thread because I received the same error message and I'm pretty much in a similar environment (parse, subclassing, swift). The line where my app crashed was this one:

let setOpts = self.thing?.settingOptions

where the variable "thing" represents a PFObject as well as "settingOptions". So I thought that maybe it was also a problem of falsely registered subclasses, although I think that's not necessary anymore in the recent Parse versions (I'm using v1.15.1). Anyway, the workaround you provided helped at first, but made my app crash at that next line:

if (self.thing?.setting != nil) {...}

and then it got me thinking...wait a minute...there were several other properties of "thing" accessed through dot notation in between which did not crash, so why again here?! When I checked back at your post it hit me right in the face. I hope everybody sees it by now because you might not believe me if I tell you...but I'm gonna anyways:

The properties we use all start with setting.

And that seems to be it. I don't know if they shouldn't start with "set" or "setti", but definitely not with "setting". As soon as I changed the name to something completely different it worked. Maybe the classname is relevant, too, but mine starts with a prefix so "setting" is only part of the name. Hope this helps ;)

Answer 3

Don't have an answer as to why it's happening but i'm using a workaround that is slightly cleaner in my mind as the workaround is only in one place. Namely using the setter and getter functionality of swift.

class SettingsModel: PFObject, PFSubclassing {

override class func initialize() {
    struct Static {
        static var onceToken : dispatch_once_t = 0;
    }
    dispatch_once(&Static.onceToken) {
        self.registerSubclass()
    }
}

static func parseClassName() -> String {
    return "Settings"
}

@NSManaged var name:String
@NSManaged var code:String
var friend:FriendsModel
    {
        get
        {
             return self["friend"] as! FriendsModel 
        }
        set
        {
             self["friend"] = newValue
        }
    }

}