RealmファイルをwatchOSにfileTransferしたときの実機で生じるエラーと解決方法 ref: http://qiita.com/hsylife/items/7dc70b52e34dd941c9e4

after

// When the file was received
    func session(_ session: WCSession, didReceive file: WCSessionFile) {

        //set the recieved file to default Realm file
        var config = Realm.Configuration()
        let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        let documentsDirectory = paths[0]
        let realmURL = documentsDirectory.appendingPathComponent("data.realm")
        if FileManager.default.fileExists(atPath: realmURL.path){
            try! FileManager.default.removeItem(at: realmURL)
        }
        try! FileManager.default.copyItem(at: file.fileURL, to: realmURL)
        config.fileURL = realmURL
        Realm.Configuration.defaultConfiguration = config

        // display the first of realm objects
        let realm = try! Realm()
        if let firstField = realm.objects(Field.self).first{
            realmLabel.setText(firstField.text)
        }
    }

before

// When the file was received
    func session(_ session: WCSession, didReceive file: WCSessionFile) {

        //set the recieved file to default Realm file
        var config = Realm.Configuration()
        config.fileURL = file.fileURL
        Realm.Configuration.defaultConfiguration = config

        // display the first of realm objects
        let realm = try! Realm()
        if let firstField = realm.objects(Field.self).first{
            realmLabel.setText(firstField.text)
        }
    }