Learning iOS Programming, 2nd Edition

Chapter 9. Using Sensors

Mobile phones aren’t just for making phone calls anymore. The iPhone, like a lot of high-end smartphones these days, comes with a number of sensors: camera, accelerometer, GPS module, and digital compass. We’re entering a period of change: more and more users expect these sensors to be integrated into the “application experience.” If your application can make use of them, it probably should.

Hardware Support

Unique among modern mobile platforms, Apple has gone to great lengths to ensure that your code will run on all of the current iOS-based devices. Yet despite this, there is still some variation in hardware between the various models (see Table 9-1).

Table 9-1. Hardware support in various iPhone, iPod touch, and iPad models

Hardware feature	iPhone					iPod touch				iPad		iPad 2
	Original	3G	3GS	4	4S	1st Gen	2nd Gen	3rd Gen	4th Gen	WiFi	3G	WiFi	3G
Cellular	✓	✓	✓	✓	✓	✗	✗	✗	✗	✗	✓	✓	✓
WiFi	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
Bluetooth	✓	✓	✓	✓	✓	✗	✓	✓	✓	✓	✓	✓	✓
Speaker	✓	✓	✓	✓	✓	✗	✓	✓	✓	✓	✓	✓	✓
Audio In	✓	✓	✓	✓	✓	✗	✓	✓	✓	✓	✓	✓	✓
Accelerometer	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
Magnetometer	✗	✗	✓	✓	✓	✗	✗	✗	✗	✓	✓	✓	✓
Gyroscope	✗	✗	✗	✓	✓	✗	✗	✗	✓	✗	✗	✓	✓
GPS	✗	✓	✓	✓	✓	✗	✗	✗	✗	✗	✓	✗	✓
Proximity Sensor	✓	✓	✓	✓	✓	✗	✗	✗	✗	✗	✗	✗	✗
Camera	✓	✓	✓	✓	✓	✗	✗	✗	✓	✗	✗	✓	✓
Video	✗	✗	✓	✓	✓	✗	✗	✗	✓	✗	✗	✓	✓
Vibration	✓	✓	✓	✓	✓	✗	✗	✗	✗	✗	✗	✗	✗
Retina Display	✗	✗	✗	✓	✓	✗	✗	✗	✓	✗	✗	✗	✗

Network Availability

We covered Apple’s Reachability code in detail in Apple’s Reachability Class in Chapter 7. We can easily determine whether the network is reachable, and whether we are using the wireless or WWAN interface:

Reachability *reach = [Reachability reachabilityForInternetConnection]; NetworkStatus status = [reach currentReachabilityStatus]; ...