I have a custom class with which i made an (swift-y) struct NSCodable. Now I want to convert that into a CKRecord in order to use CloudKit. Even though I set 'key value'-pairs when encoding my struct, it is in my understanding that the struct is converted into NSData and that you can't convert it to a Dictionary (or another key-value object). So I get the feeling that this is not the way to go.
Is there a way to make this conversion directly? Or with a step in-between (for instance converting the Data into a [String: String]- dictionary)?
NSCoding is only for going from/to the same class. Instead, write a toServerDictionary method on your custom class, including only the properties you want to send to CloudKit, and then use the result to call setValuesForKeys on a CKRecord.
You'll likely find there are properties that need to be specific types, in which case its better to make your method toServerRecord and create a CKRecord and return it. You can also have a updateWithServerRecord to set anything you receive back.
Related
I have iOS app that takes data from the server as json and then serializes them into objects of different types. Types can be complicated, can contain subtypes, can inherit, so there is no any limitations. Another thing that makes everything even more complicated is some of types are stored as AnyObject? and only in run time they are being serialized into real types accordingly to the specific rules. Something like that:
class A {
var typeName: String?
var b: AnyObject?
}
Then when it's serialized it can be done something like that:
if let someClass = NSClassFromString(typeName) as? SomeGenericType.Type{
b = someClass.init()
}
Also querying should be done on all the data. Currently I'm trying to store all of them locally, then load into memory and query there from the code. I'm using User defaults, but they have some limitations, also I needed to provide custom coding to make it work, and each time when I add a new field it turned out that I missed something in coding and nothing works. So it's pain.
Ideally I would just do some magic command and all the objects are sent to local storage no matter how complicated they are. The same to extract them from this storage. Also, user change data so I can't just store primary Json. And I don't want to covert objects back to Jason as for it's pain too.
Any suggestions?
If you want to use sqlite then You can store whole object in one row! I means you can create table with 2 columns one is id and second is your dataobject(it's data type should be blob). Then convert your whole object into data. Then store in sqlite table and retrieve it as data then convert it to object when want to use. By this way your object will remains in same format as you asked
Firebase while meant for online synching and storage can also cache everything locally in case you are offline and perform query's against the local cache. It uses JSON.
CouchDB also has a mobile version for iOS.
Both of those are over kill if your dataset is small; you can just store it as a text file and read the JSON back in. See performance characteristics here. The graph is for a 7MB file so if you are significantly less than that your load time may be minimal.
NSKeyedArchiver.archivedData(withRootObject:) is great for storing custom objects as Data objects. The only thing you need to do to be able to use this is to make your custom objects conform to NSCoding. A great example can be found here:
Save custom objects into NSUserDefaults
Once you have the Data version of the object, it can easily be stored in UserDefaults, as a property in CoreData, or even in the app's keychain entries. Depending on your use case, sensitivity of data, and how much data you intend to store, you might want to use any number of storage methods. NSKeyedArchiver.archivedData(withRootObject:) allows you to pretty much use any of them.
I've having difficulty saving an NSManagedObject in userDefaults and I'd like to know a) should I be trying to do this or is this not an appropriate approach or b) if it is an appropriate approach, how can I get it to work?
I'm writing my app in Swift 2.3 and it has a few user default options, one of which is for a default "lift" (as in weightlifting, e.g. 'bench press', 'clean and jerk', 'incline bench press'). I'm actually converting them from an enum to a Core Data entity because every lift event that the user will be able to keep track of will be one of the available lifts types (for which I'll establish the appropriate relationship).
Here's the extension with the properties:
extension Lift {
#NSManaged var liftName: String
#NSManaged var type: NSSet
}
and the Lift entity with the things Xcode is complaining about:
class Lift: NSManagedObject, NSCoding {
func encodeWithCoder(aCoder: NSCoder) {
aCoder.encodeObject(liftName, forKey: "liftName")
} // Super.init isn't called on all paths before returning from initializer
required init(coder aDecoder: NSCoder) {
// Initialization of immutable variable was never used, etc...
let liftName = aDecoder.decodeObjectForKey("liftName") as! String
}
}
I've dealt with these types of errors before so my real concern is whether or not I'm headed down the wrong path.
I've read numerous threads tonight which have taught me that I'll need to encode an object (but not specifically an NSManagedObject) to save it then unencoded it when retrieving it and that my class must conform to NSCoding and what that protocol requires. But then I've seen threads that say NSManagedObjects should NOT be stored in userDefaults, but I don't know if that's true.
I've spent a few hours on this so before I go further, can/should this be done?
No, you should not store an NSManagedObject in NSUserDefaults. Core Data is an object persistence technology, so it doesn't make sense to try and persist an NSManagedObject in some other format.
There are few alternatives you can use:
You could simply store the name of the lift in your user defaults and then query for this to get the object back from Core Data. This may not work for you if lift names aren't unique
You can add an identifier attribute to your Lift entity and store something like a UUID string in that attribute; You can then store the same string in UserDefaults. This will ensure one object is selected uniquely.
You can add a new boolean attribute to your Lift entity default and again use a query to retrieve it; You would need to ensure you only set the value to true on one lift at a time.
You can use managedObject.objectId.uriRepresentation to get a URL that you can store as a string and then use to retrieve the object later. This is probably the most complex solution and I would suggest you try one of the other options.
No, You cannot do this. You cannot save Core Data objects in User Defaults. It can only save in its DB.
This two are totally two different things. NSUserDefault stores the light pieces of data where NSManagedObject stores the light or heavy amount of data and is very fast than NSUserDefault for storing and retrieving purposes.
NSManagedObject -> NSManagedObject link to coredata.
You should it to store a large list of elements. As far your last question, there is nothing preventing you from using both Core Data and a backend to store your data. In fact, there are frameworks out there to facilitate exactly this.
NSUserDefaults -> NSUserDefaults is a class that allows simple storage of different data types. It is ideal for small bits of information you need to persist between app launches or device restarts. NSUserDefaults is not sufficient and reliable to store and query the huge amount of data. It's suggestable if you'll have a backend (database on the server) to store events and their invitees to persist consistency of user's information (if user logged in back to your app from other app supportive device then he'll get all information he stored).
NSUserDefaults supports the following data types:
NSString, NSNumber, NSDate, NSArray, NSDictionary and NSData
Hope it will help you.
Storable Types in NSUserDefaults.
The NSUserDefaults class acts very much like something called a Property List (aka plist). It may be just a fancy interface for a plist, or it may be more, I’m not entirely sure. Nonetheless, plists are limited in what kind of objects they can store. The six types plists can store are:
NSData
NSString
NSNumber
NSDate
NSArray
NSDictionary
So,you need to use in NSKeyedArchiver.
let ArchvieArr = NSMutableArray()
ArchvieArr.addObject(NSKeyedArchiver.archivedDataWithRootObject(LiftObj)).
NSUserDefaults.standardUserDefaults().setObject(ArchvieArr, forKey: "savedArray")
I've been looking for a way to serialize custom objects with NSJSONSerialization avoiding the use of third-party libraries, and I couldn't find any example. Is there any way of "automatically" create an NSDictionary and NSArray from an object, without having to create it typing in code all the object's member names yourself one by one and setting manually the values? I found a related post, but it is pretty old, things may have now changed.
Thanks
You can use KVC to ask any object for dictionaryWithValuesForKeys: which will give you a dictionary representation of the object.
If you need to change the property / key names then you want to do some mapping and (depending on what you're using the JSON for) you may find RestKit useful.
Specifically, say I have an NSManagedObject with a "statusCode" attribute set to transformable, and a reversible value transformer subclass to covert from NSStrings to NSNumbers and vice versa. The idea is to use the value transformer so that I receive JSON and a string from a "status" key in the JSON automatically maps to an NSNumber that represents that status code in an NSManagedObject. Conversely if I were to upload the NSManagedObject to a server, at that point its status attribute would be transformed from an NSNumber to a string for the JSON.
So far so good. But, what if I also want to be able to get a simple int out of the NSManagedObjec's status property, so that I can AND it with enums in code?
That is, I'd lie to cover 3 cases:
myManagedObject.status = [JSONResponse valueForKey:#"status"] (should use transformer to do NSString -> NSNumber)
[JSONforUpload setValue:myManagedObject.status forKey:#"status"] (should use transformer to do NSNumber->NSString)
From elsewhere in code, anything along the lines of: if(myManagedObject.status & statusInProgress) ... where statusInProgress is an enum.
I'm thinking I could temporarily disable the value transformer, however I have no idea if the NSManagedObject has a reference to it, or if I should disable it from the NSValueTransformer class, which apparently keeps a table of registered transformers?
I know that for the 3rd case I could just do [myManagedObject.status intValue] and then do the bitwise comparison, but I'm wondering if there's any way I can have the intValue] be returned automagically, from the user of this object's point of view.
Any ideas?
Why don't you just write two additional methods for the JSON transform and leave the property as integer? Then you'd have the best from both worlds.
One approach would be to add a property to the transformer so that it switches between string and enum reversed values. That would work, though I ended up doing a enum<->string transformer and not using it over a transformable attribute (instead I left the managed object's attribute as int) but rather instantiating it only for the JSON <-> object conversion. After that, throughout code I just use the int attribute as is.
Assuming that this entity has its own distinct managed object subclass, you could also simply add another pair of accessor methods to the class to encapsulate the conversion between NSNumber and int values. (Or add a transient attribute, if it needs to be part of the model. But you'd still need to write custom accessors to synch up the values.)
Right now I am using ArrayCollection. But I want to change that to Set as I want make sure do duplicate values come.
var addressList:ArrayCollection = new ArrayCollection();
One way is I can use Dictionary and store addresses as a key. And I can just use keys to iterate.
But I am looking for Java HashSet like implementation.
You want to download Polygonal Data Structures. The swc contains a HashSet. If you want Java-style template syntax for Flash, you should also check out Haxe.
The AS3 equivalent to HashMap or HashSet is the Dictionary class, and to a lesser extent, the Object class. Object keys are stored as strings, while with Dictionary the keys are objects. You can't have duplicate entries with either. Are you looking for a specific implementation other than that?