I think this is a probably repeat question.
I am new to ios and and I am trying to learn so I don't expect response in actual codes. I still want to write them myself.
Here's what I have done so far:
I wrote codes to make web api calls, authenticate and pull json data.
I've figured out how to parse json data that I pulled from web.
I have made tableview controller.
Challenge: How do I get the parsed Json data to tableview controller?
Do I:
- save it locally into like NSUSERDefaults variable?
- save it to a global variable shared by controller and my model?
- at the end of the parsing json data do a return so that it will be saved into viewController?
- or none of the above and do ______________ (insert your answer)
What's the cleanest way to do this? The table will initially have like 20 rows but as you pull down you will get more rows.
Best way to save data on model class while parsing and store this class objects in an array and in cellforrowatindexpath get objects of model class from array and show data using these objects.
Related
I need to cache json data from API in swift.
So I researched a Lot & get to this Post.
I tried to implement the Option 1 in my App. But the Custom manager always returned nil. I don't know why?
After that I got AwesomeCache. It says that it an do Awesome API Caching.
But I don't know how to implement this?
I referred this Issue. Still I can't figure it Out.
This is how my Current implementation Looks without Cache:
Alamofire.request(.GET, "http://api.androidhive.info/volley/person_array.json")
.responseJSON { (_, _, data, _) in
let json = JSON(data!)
let catCount = json.count
for index in 0...catCount-1 {
let name = json[index]["name"].string
println(name)
}
Please suggest me the Best way to Cache JSON from API ?
Thanks in Advance!
UPDATE
These are my requirements
Fetch the JSON from the API & Parse the JSON data. These can be done with the help of Alamofire & SwiftyJSON
I will populate the parsed data in the Table View. It works when the user is in Online.
But I want to show the data in the Table when the user is in offline too.
So I need to save the Parsed data or the JSON data in my cache & I need to refresh or expire the cache within a week or days.
I don't prefer to store the JSON in my disk because it will be updated.
Please suggest me the Best way to achieve this...
You have many tools already at your disposal.
NSURLCache
All your requests are already stored in the NSURLCache in the NSURLSessionConfiguration on the NSURLSession stored inside the sharedInstance of the Alamofire Manager. Those stored requests already follow all the caching policy rules provided by the servers you are hitting. You can control the caching behavior by setting the requestCachePolicy on your own custom NSURLSessionConfiguration. I'd also suggest you read through this awesome NSHipster article that walks you through the ins and outs of NSURLCache and how to control it.
Creating custom Manager objects is covered in the current Alamofire docs.
Downloading JSON to Disk
You can also download the JSON directly to disk using Alamofire.download instead of using Alamofire.request. This will download the payload to a fileURL that you provide in the destination closure. This would give you full control over the caching of the file after that point. You would need to create your own caching policy around these files afterwards if you wanted to follow the caching header rules provided by the server.
Populating Table View
Once you have your data downloaded to disk, you need to load it into an NSData blob and parse it into JSON to populate your table view. This should be pretty straight forward. You need the destination NSURL that you specified to Alamofire when you started your download. Then load the file data into an NSData blob. Finally, use NSJSONSerialization to convert the NSData object into a JSON AnyObject which can be parsed into model objects to populate your table view.
Obviously you don't "have" to parse the JSON into model objects, but this helps protect your table view from malformed JSON data.
Storing JSON for Offline Usage
If you stick with this approach, you'll need to track your cache expiration dates in something like CoreData or SQLite. You can do this by either caching the paths to the JSON files on disk, or store the model objects directly in CoreData or SQLite. This could get fairly complicated and I would not recommend this approach unless you absolutely don't want to cache your model objects.
Offline Usage
Generally, if you need to cache data for offline usage, you want to store your model objects in something like CoreData. You would use the Alamofire request method coupled with a responseJSON serializer to parse the data into JSON. Then you would convert the JSON into model objects. From there, you'd save your model objects in CoreData, then finally populate your table view with the model objects.
The nice thing about this approach is that you have all your model objects cached in the case that your table view is accessed when the device is offline. Coupling this design with queries to your NSURLCache to see if your request is cached let's you avoid unnecessary server calls and parsing logic when you already have your model objects generated.
Given the updates to your original question, I would recommend this approach.
You can use this cache open source. It cache data on disk and memory. Can cache many swift type, and custom class which inherit NSObject and conform NSCoding protocol.
https://github.com/huynguyencong/DataCache
To implement:
First, it use NSCache for mem cache. NSCache use like a dictionary.
Second, save cache to disk, use NSFileManager methods.
What would be the best practise and best for user experience to achieve the following?
1:) Retrieve data from JSON
2:) Store in Core Data
3:) Display in UITableViewController
Do i store the JSON first, then populate the table using the stored data? OR Do i store it in the Core Data (background process) and populate the table using the JSON for the first time?
I want the user to be presented with a UITableview with minimum load time.
Thanks
This is what I would do:
Create your Core Data database and model.
Create a data access layer that will contain the read and write methods for each of your objects
In the read functions you can query the core data, if there is data then return that. Then in the background call the web server and and update your core data with the new JSON.
If there is no data go and request it from the web server, populate your core data tables using the JSON and then return the data from the core data so it is always consistent.
You can also have a last update date on your data so you are only requesting the new data from the web server that isnt already in your local core data DB. This will reduce the amount of data coming down to your ios device.
If you want minimum load time then I'd serve from JSON and that save to CoreData afterwards. That way the user can see content straight away without first having to wait for all the data to be saved (and parsed).
The course of action in this matter heavily depends on:
A. The amount of JSON data you are downloading
B. How effective your backend is at only sending necessary JSON results (rather than sending everything in bulk)
C. How you are attaching Core Data to your UITableViewController.
I recently made a pretty big project that does exactly this, which involved fetching a pretty big chunk of JSON, parsing it, and inserting it into Core Data. The only time there is any delay is during the initial load. This is how I accomplished it:
Download JSON. Cast as [[String: AnyObject]]: if let result = rawJSON as? [[String: AnyObject]] {}
Check to see if IDs for objects already exist in Core Data. If that object already exists, check if it needs update. If it doesn't exist, create it. Also check if IDs have been deleted from the JSON, if so remove them from.
Use NSFetchedResultsController to manage data from Core Data and populate the UITableView. I use NSFetchedResultsController rather than managedObjectContext.executeFetchRequest() because NSFetchedResultsController has delegate methods that are called every time the managedObjectContext is updated.
I'm using Parse as the backend for my app. My app will be used in the field where service will nonexistent or spotty at best so I need to store information offline. I currently save data for the user in a plist in the background (Title, location coordinates, notes, additional data). Since Parse's current iOS offline saving is fairly poor (From what I've read), I was hoping to get around it by creating an array or dictionary from the plist and upload that to Parse by giving it an array once the user is back in cell range.
As it occurs now, when I upload the array, it simply puts the entire contents of the array in a single cell in the database. Is there a way to parse the array and create a new row for each entry/object in the array?
I may have overlooked a better way to do this. If someone has a suggestion I would appreciate it!
I solved it. I iterated through the array using a for loop and added each index as a separate object.
I watched a video tutorial on CoreData. I saw a that an option
Uses Lazy fetching
To map an Object Model with Array Controller.
But did not understand what is Lazy fetching?
That means that data would be actually fetched (automatically) not a the time of request, but at the time when controller would ask for data. For example consider large tableview with thousands of lines - they are not fetched all at the same time when request is executed, rather they are fetched by small parts dynamically when users scrolls tableview.
I ve a JS array, comprising multiple JS objects.
I want to convert JS array to JSON type, & pass that to controller (using AJAX - POST call).
So that I can retrieve the values from the Array of Objects, in my controller & save them in DB.
NB: I ve tried using $.stringify(myArry), but its not able to send data to controller in JSON format. Also I cant use $.toJSON(myArray), as I m not allowed to include a new plugin in our solution. :(
Plz suggest me any other idea.
Else if anyone can let me know how to deserelize the array in cotroller, that I ve sent by using $.stringify(myArry), that would also great.
Something like
var result = JavaScriptConvert.DeserializeObject(inputContent, JsonDataType);
Per this post, it looks like you'll have to add another plug-in:
JSON stringify missing from jQuery 1.4.1?
The Google solution looks good: http://code.google.com/p/jquery-json/
Or just use the JSON object from Crockford: https://github.com/douglascrockford/JSON-js