Creating a flexible API class in Swift - ios

Question

I'm trying to design an API helper function for an app. The idea is that I'll be able to call the function from a viewController, using code such as:
let api = APIController();
api.request("get_product_list")
api.delegate = self
Here's the class so far:
import Foundation
protocol APIControllerProtocol {
func didReceiveAPIResults(originalRequest: String, status: Bool, data: String, message: String)
}
class APIController {
var delegate: APIControllerProtocol?
let url = "https://example.co.uk/api.php"
let session = NSURLSession.sharedSession()
let appID = "EXAMPLEAPPID";
let deviceID = "EXAMPLEDEVICE"
func request(req:String)-> Void {
let urlString = "\(url)?request=\(req)"
let combinedUrl = NSURL(string: urlString)
let request = NSMutableURLRequest(URL: combinedUrl!)
request.HTTPMethod = "POST"
let stringPost="app_id=\(appID)&device_id=\(deviceID)"
let data = stringPost.dataUsingEncoding(NSUTF8StringEncoding)
request.timeoutInterval = 60
request.HTTPBody=data
request.HTTPShouldHandleCookies=false
let task = session.dataTaskWithRequest(request) {
(data, response, error) -> Void in
do {
let jsonData = try NSJSONSerialization.JSONObjectWithData(data!, options:NSJSONReadingOptions.MutableContainers ) as! NSDictionary
let statusInt = jsonData["status"]! as! Int
let status = (statusInt == 1)
let data = String(jsonData["data"])
let message = String(jsonData["message"])
self.delegate?.didReceiveAPIResults(req,status: status,data: data,message: message)
} catch _ {
print("ERROR")
}
}
task.resume()
}
}
The difficulty I'm having is that the 'data' parameter might one of the following:
A string / number, such as the number of purchases a customer has made
An array of items, such as a list of products
A dictionary, such as the customer's details
I've set the data parameter to String as that allowed me to do some testing, but then converting it back into something usable for a tableView got very messy.
Are there any experts on here that can advise me the best way to do this? Perhaps showing me how I'd use the results in a cellForRowAtIndexPath method? Here's an example response from the API, in case it's useful:
{
"status":1,
"message":"",
"cached":0,
"generated":1447789113,
"data":[
{"product":"Pear","price":0.6},
{"product":"Apple","price":0.7},
{"product":"Raspberry","price":1.1}
]
}

Answer 1

One function doing too many things at once makes a really messy code. Also you don't want too many if statements or enums - your View controller will grow really fast.
Id suggest splitting request and parse logic. Your API class would be then responsible only for requests. It would return data to another class, that would be responsible for parsing. Then in the Parser class you could add methods like toDictionary() or toArray(), toArrayOfClasses() and so on. That would be the basic API structure.
If you want to expand it a little bit, you could add another class layer that would handle all that logic so your View Controller doesn't know if it uses API or another data source - this way you could easy implement new things in the future, like Core Data or migrate from your API class to some framework, maybe Parse.com - this layer gives you flexibility.
Example structure:
API - requests
Parser - parsing API response
DataManager - Send request to API and return parsed response.
or if you don't want this third point, you can just request & parse in the view controller.