CoreBluetooth: unable to discover characteristics for discovered peripheral

I have written some CoreBluetooth code, I can discover the devices but I seem to be unable to discover the characteristics for peripherals that I discover. Does anyone have a good sample code that I can use to verify my code?

This is what I wrote:

#import "ViewController.h"
@property(nonatomic, strong) CBCentralManager* centralmanager;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.centralmanager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];
}

- (void)centralManagerDidUpdateState:(CBCentralManager *)central
{
    CBCentralManagerState currentState =  central.state;
    NSLog(@"state %i", currentState);

    switch (central.state)
    {
        case CBCentralManagerStatePoweredOn:
        {
            NSDictionary *options = @{
                                      CBCentralManagerScanOptionAllowDuplicatesKey: @YES
                                      };
            [self.centralmanager scanForPeripheralsWithServices:nil options:options];
            NSLog(@"I just started scanning for peripherals");
            break;
        }
    }
}
- (void)centralManager:(CBCentralManager *)central
  didConnectPeripheral:(CBPeripheral *)peripheral{
    NSLog(@"connected!");
}

- (void) centralManager:(CBCentralManager *)central
  didDiscoverPeripheral:(CBPeripheral *)peripheral
      advertisementData:(NSDictionary *)advertisementData
                   RSSI:(NSNumber *)RSSI
{
    [self.centralmanager connectPeripheral:peripheral options:nil];

    if ([[advertisementData description] containsString:@“keyword”]) {


         NSLog(@"peripheral count %lu", (unsigned long)[peripheral.services count]);
         [peripheral.services count];
       for (int i=0; [peripheral.services count]; i++) {
            for (CBService *s in peripheral.services) {
                [peripheral discoverCharacteristics:nil forService:s];
            }
        }
    }
}


- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error{
    NSLog(@"did discover characteristic for service");
}

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSArray *)serviceUuids{
    NSLog(@"discovered a peripheral's services: %@", serviceUuids);
}

Have a look here: Sample Code

Basically the process is:

1. Scan for devices
2. Discover device
3. Connect to device
4. Ask device for services
5. Ask services for characteristics
6. Write to, read from, or get notified by characteristics

Subsequently you don't have to search for and discover devices, as previously discovered devices can be retrieved from cache and connected to directly.

Edit: --------------------

Read example: [aPeripheral readValueForCharacteristic:aChar];

Notify example: [aPeripheral setNotifyValue:YES forCharacteristic:aChar];

Both of these calls will result in the - (void) peripheral:(CBPeripheral *)aPeripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error- function to get called when the BLE device returns a value. When using notify, this callback get called automatically every time the device updates its value for that characteristic.