1. Топ-10 ошибок
при разработке iPhone-приложения
Top 10
iPhone Application Development Mistakes
Alexander Kaverin
iPhone developer at Ciklum for iAgentur.ch

2. Section A
User Interface

3. 1. Not following HIG
• HIG stands for iPhone Human Interface Guidelines
http://developer.apple.com/iphone/library/documentation/UserExperience/
Conceptual/MobileHIG/
• Providing a consistent visual experience has always
been important for the Mac - so it is for iPhone

4. Standard controls offered by iPhone SDK

5. 2. Overusing Interface Builder
• Interface Builder, despite its extensive
functionality, is not a tool to create complete visual
design
• IB may not contain some essential settings
• IB is good for static interface objects. For dynamic
objects coding is better
• Unarchiving a .xib file is more resource-consuming
than setting properties in code

6. 2. Overusing Interface Builder

7. 3. Slow responsiveness
• Bad practice:
• preloading too much data in advance
• complex view hierarchy
• filling invisible areas of views
• displaying large lists when they are not requested
• Memory usage also affects UI responsiveness

8. 3. Slow responsiveness
• Good practice:
• loading larger portions of data only on user’s demand
• you may even show an empty screen for a while before
the data is loaded
• move non-UI operations to separate threads
• Remember: the user always expects to see (almost)
immediate reaction to his actions

9. Section B
Application Design

10. 4. Relying on a fast network
performance
• iPhone devices can operate in Wi-Fi, 3G, EDGE and GPRS
networks
• Supporting only Wi-Fi network may lead to malfunctioning
and even to AppStore rejection.

11. 4. Relying on a fast network
performance
If an Application requires or will have access to the cellular network, then additionally such
Application:
• Must comply with Apple's best practices and other guidelines on how Applications
should access and use the cellular network;
• Must not in Apple's reasonable judgment excessively use or unduly burden network
capacity or bandwidth;
• May not have Voice over Internet Protocol (VoIP) functionality using the cellular
network.
Paragraph 3.3.19 of the iPhone SDK agreement

12. 4. Relying on a fast network
performance
• Solutions:
• Display slow connection alert.
Use SCNetworkReachabilityGetFlags
- (BOOL)isWifiAvailable {
BOOL wifi = NO;
const char *host_name = "google.com";
SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(
NULL, host_name);
SCNetworkReachabilityFlags flags;
SCNetworkReachabilityGetFlags(reachability, &flags);
CFRelease(reachability);
if (flags == 2) {
wifi = YES;
}
return wifi;
}

13. 4. Relying on a fast network
performance
• Solutions:
• UIRequiresPersistentWiFi key in Info.plist

14. 5. Battery life
• Battery life and memory / CPU usage are the Apple’s
official reasons to disallow background processes
• Network data transfer
• Operations over Wi-Fi consume less power than
operations over mobile networks
• Inefficient usage of CoreLocation

15. 6. Resigning active state of the
application
• The application becomes inactive:
• when accepting a call
• when the iPhone screen goes to sleep
• Resetting application in this situation is not the best
practice

16. Section C
Objective-C and Cocoa

17. 7. Breaking the MVC pattern
Model - View - Controller

18. 8. Bad memory management

19. 8. Bad memory management
• iPhone Objective-C runtime, unlike Mac OS (10.5 +) does
not support garbage collection
• Following retain/release paradigm and maintaining object
ownership rules is mandatory
• Use Instruments to debug memory issues effectively

20. 9. Retain cycle
myView myDelegate
MyViewClass : UIView { MyDelegateClass : NSObject {
... ...
id _delegate; UIView *_view;
} }
@property (retain) delegate; @property (retain) view;
... ...
- (void) dealloc { - (void) dealloc {
[_delegate release]; [_view release];
... ...
} }

21. 9. Retain cycle
myView myDelegate
1 1

22. 9. Retain cycle
myView myDelegate
1 1
self.delegate = myDelegate
[_delegate retain]
2

23. 9. Retain cycle
myView myDelegate
1 1
self.delegate = myDelegate
[_delegate retain]
2
myDelegate.view = self
[_view retain]
2

24. 9. Retain cycle
myView myDelegate
1 1
self.delegate = myDelegate
[_delegate retain]
2
myDelegate.view = self
[_view retain]
2
[myDelegate release]
[myView release]
1 1

25. 9. Retain cycle
myView myDelegate
MyViewClass : UIView { MyDelegateClass : NSObject {
... ...
id _delegate; UIView *_view;
} }
@property (retain) delegate; @property (retain) view;
... ...
- (void) dealloc { - (void) dealloc {
[_delegate release]; [_view release];
... ...
} }

26. 9. Retain cycle
myView myDelegate
MyViewClass : UIView { MyDelegateClass : NSObject {
... ...
id _delegate; UIView *_view;
} }
@property (assign) delegate; @property (retain) view;
... ...
- (void) dealloc { - (void) dealloc {
... [_view release];
} ...
}

27. 9. Retain cycle
myView myDelegate
1 1
self.delegate = myDelegate
myDelegate.view = self
[_view retain]
2
[myDelegate release]
[_view release]
0
1
[myView release]
0

28. 10. Usage of private API
• Not recommended by Apple
• May become a reason of rejection from the AppStore
• Private API may change at any OS / SDK release without
notice

29. Q&A