Getting BLE (dynamic) data on another screen - iOS swift - ios

Question

I'm brand new to iOS + BLE development. I'm trying to do something very basic - connecting a BLE device to an app. There are two screens to this app.
First screen is where it detects BLE status "ble_Status" label - if BLE is ON/OFF on
the device. If the device is receiving advertisement signals from
BLE chip, then connect to BLE chip. Currently, "Connect" and "Skip Page" navigate to second screen as a show Action Triggered Segue.
Second screen has one label "amt_consumed" - this is where the ble characteristic data needs to be displayed.
Second screen is where the characteristic data needs to be displayed
on "amt_consumed" label.
I made a new cocoa class and use prepareforsegue to pass data to the next screen. It works but only shows one value. The value from ble is dynamic and changes accordingly on the first screen but on the second screen, amt_consumed shows the value at the moment the segue is triggered. How do I keep this value updating constantly?
Here's the code:
ViewController.swift
import UIKit
import CoreBluetooth
import Foundation
//Define BLE UUID Variables
var bleServiceUUID: CBUUID!
var bleCharUUID: CBUUID!
class ViewController: UIViewController, CBCentralManagerDelegate, CBPeripheralDelegate {
//Define BLE Manager/Peripheral Variables
var cManager : CBCentralManager!
var blePeripheral : CBPeripheral!
//Define BLE Outlets
#IBOutlet weak var ble_Status: UILabel!
#IBOutlet weak var amt_consumed: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
//------->BLE<--------//
bleServiceUUID = CBUUID(string:"FFF0")
bleCharUUID = CBUUID(string:"FFF1")
cManager = CBCentralManager(delegate: self, queue: nil)
//------->BLE END<--------//
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
//-------->BLE CODE START<-------//
//Check HW for BLE
func centralManagerDidUpdateState(central: CBCentralManager!) {
self.ble_Status.text = "Searching for BLE Devices"
switch (central.state) {
case .PoweredOff:
self.ble_Status.text = "BLE Off"
case .PoweredOn:
self.ble_Status.text = "BLE ON and searching..."
central.scanForPeripheralsWithServices(nil, options: nil)
default:
self.ble_Status.text = "Cannot find"
}
}
func centralManager(central: CBCentralManager!, didDiscoverPeripheral peripheral: CBPeripheral!, advertisementData: (NSDictionary), RSSI: NSNumber!) {
if peripheral.name == "Nishant's Flow Bottle" {
println("Discovered: \(peripheral.name)")
ble_Status.text = "Discovered: \(peripheral.name)"
self.blePeripheral = peripheral
cManager.stopScan()
self.cManager.connectPeripheral(peripheral, options: nil)
}
else {
central.scanForPeripheralsWithServices(nil, options: nil)
}
}
// Check out the discovered peripherals to find Sensor Tag
func centralManager(central: CBCentralManager!,didConnectPeripheral peripheral: CBPeripheral!)
{
peripheral.delegate = self
peripheral.discoverServices([CBUUID(string: "0F37491A-AA8E-51B4-0252-F5F0857134D9")])
self.ble_Status.text = "Connected to \(peripheral.name)"
//---discover the specified service---
var services = [bleServiceUUID]
peripheral.discoverServices(services)
}
// If disconnected, start searching again
func centralManager(central: CBCentralManager!, didDisconnectPeripheral peripheral: CBPeripheral!, error: NSError!) {
self.ble_Status.text = "Disconnected"
central.scanForPeripheralsWithServices(nil, options: nil)
}
//---fired when services are discovered---
func peripheral(peripheral: CBPeripheral!,
didDiscoverServices error: NSError!) {
for service in peripheral.services {
println(
"P: \(peripheral.name) - Discovered service S:'\(service.UUID)'")
if service.UUID == bleServiceUUID {
//---discover the specified characteristic of the service---
var characteristics =
[bleCharUUID]
//---discover the characteristics of the service---
peripheral.discoverCharacteristics(
characteristics, forService: service as CBService)
}
}
}
func peripheral(peripheral: CBPeripheral!,
didDiscoverCharacteristicsForService service: CBService!,
error: NSError!) {
// 0x01 data byte to enable sensor
var enableValue = NSInteger(1)
for characteristic in service.characteristics {
//---look for the characteristic that allows you to subscribe to---
let thischaracteristic = characteristic as CBCharacteristic
if thischaracteristic.UUID == bleCharUUID {
//---subscribe to the characteristic---
self.blePeripheral.setNotifyValue(true, forCharacteristic: thischaracteristic)
}
blePeripheral.readValueForCharacteristic(thischaracteristic)
}
}
func peripheral(peripheral: CBPeripheral!, didUpdateValueForCharacteristic characteristic: CBCharacteristic!, error: NSError!) {
if var data :NSData = characteristic.value {
output("Data", data: characteristic.value)
}
}
func output(description: String, data: AnyObject){
println("\(description): \(data)")
amt_consumed.text = "\(data)"
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
if (segue.identifier == "btnSubmitSegue") {
var svc = segue.destinationViewController as NextScreen;
svc.dataPassed = CharReadData.text
}
}
}
Nextscreen.swift
import UIKit
class NextScreen: UIViewController {
#IBOutlet weak var amt_consumed: UILabel!
var dataPassed: String!
override func viewDidLoad() {
super.viewDidLoad()
amt_consumed.text = dataPassed
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}