thatjuan thatjuan - 2 months ago 32x
Swift Question

How to validate values before creating Realm object (in RealmSwift)

My application code gets JSON data from a server, converts it to a Dictionary and then uses that to hydrate and attempt to save a RealmSwift object with a matching schema.

I ran into a crash caused by a

value coming into a field that was declared as
in the model.
was thrown.

As suggested in this thread, one doesn't simply try to catch

My question is, is that answer correct? And, if so, what is the correct way to prevent a crash when an unexpected value is found? Isn't there some sort of validation mechanism that I can run on all of the values before attempting to set them?


I ended up writing an extension to handle this. At the moment I'm only validating numbers and dates, but the switch statement could check every single property type easily.

extension Object {

    public convenience init( withDictionary rawData: [String:AnyObject] ) {

        var sanitizedData = rawData

        let dynamicSelf = self.dynamicType

        let schema = dynamicSelf.sharedSchema()

        for property in {

            guard let value = sanitizedData[] else { continue }

            var isValid = true

            switch property.type {

                case .Double:

                    let val = Double(String(value))

                    if val == nil || val!.isNaN {
                        isValid = false

                case .Float:

                    let val = Float(String(value))

                    if val == nil || val!.isNaN {
                        isValid = false

                case .Int:

                    if Int(String(value)) == nil {
                        isValid = false

                case .Date:

                    if Int64(String(value)) == nil {

                        isValid = false

                    } else {

                        sanitizedData[] = NSDate(timeIntervalSince1970: value.doubleValue / 1000)




            if !isValid {

                log.error( "Found invalid value: \(value) for property \( of \(dynamicSelf)" )




        self.init( value: sanitizedData )