How to get data in NSUserDefaults when offline from Parse - swift

Question

I have a project that find objects in Parse as an Array and gets it when the app finish launches. But it can't get the info when there are no network connections so i'm thinking to use NSUserDefaults and firstly save the data to NSUserDefaults and get from NSUserDefaults when it is offline.
Can somebody give me a example of logic?
this is the code i wrote and i don't know how to get it when it's offline.
the Array the i want to append the data from Parse will be [[String]].
let userDefaults = NSUserDefaults.standardUserDefaults
let query = ClassSub.query()
query.whereKey("nameOfData", containsString: "testString")
query!.findObjectsInBackgroundWithBlock { (busObjects: [PFObject]?, error: NSError?) -> Void in
if error != nil {
print(error)
}
for object in testObjects! {
let testData = object["arrayData"] as? [[String]]
for i in 0..<testData!.count {testData
testArrayappend(testData![i])
self.userDefaults.setObject(NSKeyedArchiver.archivedDataWithRootObject(testData[i]), forKey: "test-time")
}
}
}
the data type in Parse is [[String]] and it looks like [["one","two"],["one","three"],["one","four"]]

Answer 1

i think it's better for you to use parse ios SDK local data store. The local data store allows you to pin your parse objects into a local database and then when you are out of network you can still get the data from your local database. Another huge advantage is the saveEventually feature which allows you to save objects while you are offline and then sync them back to the server as soon as you go online.
In order to use the local data store feature you need to do the following steps:
Enable local data store in parse config
let configuration = ParseClientConfiguration {
$0.applicationId = "{PARSE_APP_ID}"
$0.server = "http://localhost:1337/parse"
$0.localDatastoreEnabled = true
}
Parse.initializeWithConfiguration(configuration)
If you want to query from the local data store (while you are offline) you just need to call an additional function before calling the findObjectsInBackground so your code should look like the following:
let query = PFQuery(className: "MyParseObjectClassName")
// if you are in offline mode then make sure the query
// will access your local data store and not to the server
if (offlineMode){
query.fromLocalDatastore()
}
query.findObjectsInBackgroundWithBlock {
(objects: [PFObject]?, error: NSError?) -> Void in
// do something with the result
}
When you are using local data store you are required to pin the objects that are fetched from your server. In order to pin an object simply call to pinInBackground() which exist under your PFObject. You can also use pinAllInBackground() to pin multiple objects to your local data store in one call. In order to pin your objects please do the following:
let query = PFQuery(className: "MyParseObjectClassName")
// if you are in offline mode then make sure the query
// will access your local data store and not to the server
if (self.offlineMode){
query.fromLocalDatastore()
}
query.findObjectsInBackgroundWithBlock {
(objects: [PFObject]?, error: NSError?) -> Void in
if (!self.offlineMode){
// pin all objects
PFObject.pinAllInBackground(objects)
// pin only first object
let obj = objects?.first
obj?.pinInBackground()
}
}
Now in order to know when you are offline or online i recommend you to use Reachability library.
This library provides you two blocks: when you are online and when you are offline. Using those blocks you can determine when your app is connected to the internet and when it doesn't. So when it is not connected to the internet you need to set the offlineMode flag to be true and from now on all the queries will work against your local database otherwise it will work against your server.