I gave this talk at iPhone Dev Con in Boston, April 2011. It covers making HTTP requests using ASIHTTPRequest, UITableViews with remote images, caching patterns, and API design tips.

1. Effective Network
Programming
Techniques
for Ios
i P h o n e D e v C o n
B o s t o n 2 0 1 1

2. Ben Scheirman
Director of Development
ChaiONE
Houston, TX
ben@scheirman.com
@subdigital
http://flux88.com

4. Why is this
important?
99% of the apps we write are not self-
contained
Doing it wrong is terrible for the user’s
experience

5. Example 1:
The Stuttery Scroller

6. Example 1:
The Stuttery Scroller
Accessing netw
ork on the
main thread

7. Example 2:
The Perpetual Loader

8. Example 2:
The Perpetual Loader
...
oug h data
cach ing en
Not

9. The Slow Loader

10. The Slow Loader
Loading too mu
ch data...

11. Example 3:
Stale Toast

12. Example 3:
Stale Toast
ow up
ta do esn't sh
New da ht away...
rig

13. What we’ll cover
ASIHTTPRequest
UITableView with
ProgressTracking
remote images
download/upload
progress
Leveraging HTTP
API Design Tips
Caching Patterns
Large File Transfer

14. ASI HTTP Request
http://github.com/pokeb/asihttprequest

15. Installation
Copy Files into your project
Copy Reachability
Link in Frameworks

16. Usage

17. Usage
#import “ASIHTTPRequest.h”

18. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {

19. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];

20. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];

21. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];

22. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];
[request setDelegate:self];

23. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];
[request setDelegate:self];
[request startAsynchronous];

24. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];
[request setDelegate:self];
[request startAsynchronous];
}

25. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];
[request setDelegate:self];
[request startAsynchronous];
}
- (void)requestDidComplete:(ASIHTTPRequest *)request {

26. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];
[request setDelegate:self];
[request startAsynchronous];
}
- (void)requestDidComplete:(ASIHTTPRequest *)request {
//when requesting text (xml, json, etc)

27. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];
[request setDelegate:self];
[request startAsynchronous];
}
- (void)requestDidComplete:(ASIHTTPRequest *)request {
//when requesting text (xml, json, etc)
NSString *body = [request responseString];

28. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];
[request setDelegate:self];
[request startAsynchronous];
}
- (void)requestDidComplete:(ASIHTTPRequest *)request {
//when requesting text (xml, json, etc)
NSString *body = [request responseString];
//when requesting binary data

29. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];
[request setDelegate:self];
[request startAsynchronous];
}
- (void)requestDidComplete:(ASIHTTPRequest *)request {
//when requesting text (xml, json, etc)
NSString *body = [request responseString];
//when requesting binary data
NSData *data = [request responseData];

30. Usage
#import “ASIHTTPRequest.h”
- (void)fetchCustomers {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setMethod:@”GET”];
[request setDelegate:self];
[request startAsynchronous];
}
- (void)requestDidComplete:(ASIHTTPRequest *)request {
//when requesting text (xml, json, etc)
NSString *body = [request responseString];
//when requesting binary data
NSData *data = [request responseData];
}

31. UITableView
Loading images for each row
Don't make blocking network calls in
tableView:cellForRowAtIndexPath:
Leverage NSOperationQueue & a local cache
Fetch images in the background, reload the row
in question

32. Leveraging HTTP
Request Response
200 OK
GET /resource
{resource:"hello"}
GET /resource
304 NOT MODIFIED
If-Modified-Since: 03-16-2010 16:10:00
200 OK
E-Tag: 000ea9512912
GET /resource
{resource:"hello"}
GET /resource
304 NOT MODIFIED
If-None-Match: 000ea9512912

33. Caching
Fresh Data User Experience

34. Caching
Fresh Data User Experience

35. Caching
Cache Storage Policy
Permanent
Session
Cache Policy
ASIAskServerIfModifiedWhenStaleCachePolicy
ASIAskServerIfModifiedCachePolicy
ASIOnlyLoadIfNotCachedCachePolicy
ASIDontLoadCachePolicy
ASIFallbackToCacheIfLoadFailsCachePolicy

36. Enabling the Cache
[ASIHTTPRequest setDownloadCache:[ASIDownloadCache sharedChache]];
//or per request
[request setDownloadCache:[ASIDownloadCache sharedCache]];

37. Checking if Content
exists in the cache
#import "ASIHTTPRequest.h"
#import "ASIDownloadCache.h"
- (void)fetchImage {
NSURL *url = ...
NSData *cacheData = [[ASIDownloadCache sharedCache]
cachedDataForUrl:url];
//do something with cachedData
}
#import "ASIHTTPRequest.h"
#import "ASIDownloadCache.h"
- (void)requestDidFinish(ASIHTTPRequest *)request {
if ([request didUseCachedResponse]) {
//response was served from the cache!
}
}

38. Tracking Progress
Set the upload/download progress delegate of
a request
smart enough to bind directly to a
UIProgressView
For large downloads, turn on
showAccurateProgress in order to get better
precision over progress updates

39. Uploading/
Downloading Large
Files
Reduce memory overhead by streaming
directly to/from disk

40. Uploading/
Downloading Large
Files
Reduce memory overhead by streaming
directly to/from disk
#import “ASIHTTPRequest.h”

41. Uploading/
Downloading Large
Files
Reduce memory overhead by streaming
directly to/from disk
#import “ASIHTTPRequest.h”
- (void)fetchDatabase {

42. Uploading/
Downloading Large
Files
Reduce memory overhead by streaming
directly to/from disk
#import “ASIHTTPRequest.h”
- (void)fetchDatabase {
NSURL *url = [NSURL URLwithString:...];

43. Uploading/
Downloading Large
Files
Reduce memory overhead by streaming
directly to/from disk
#import “ASIHTTPRequest.h”
- (void)fetchDatabase {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];

44. Uploading/
Downloading Large
Files
Reduce memory overhead by streaming
directly to/from disk
#import “ASIHTTPRequest.h”
- (void)fetchDatabase {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];

45. Uploading/
Downloading Large
Files
Reduce memory overhead by streaming
directly to/from disk
#import “ASIHTTPRequest.h”
- (void)fetchDatabase {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];
[request setDownloadDestinationPath:...];

46. Uploading/
Downloading Large
Files
Reduce memory overhead by streaming
directly to/from disk
#import “ASIHTTPRequest.h”
- (void)fetchDatabase {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];
[request setDownloadDestinationPath:...];
[request startAsynchronous];

47. Uploading/
Downloading Large
Files
Reduce memory overhead by streaming
directly to/from disk
#import “ASIHTTPRequest.h”
- (void)fetchDatabase {
NSURL *url = [NSURL URLwithString:...];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];
[request setDownloadDestinationPath:...];
[request startAsynchronous];
}

48. Tracking progress
of multiple requests
ASINetworkQueue
requests are NSOperations, just add them
need to explicitly start the queue
will perform a HEAD request for each to
calculate total size
reports progress similar to ASIHTTPRequest

49. API DESIGN TIPS
Don't couple your API to your internal server model

50. API DESIGN TIPS
Build in Versioning

51. API DESIGN TIPS
Record Client Device Info
Device Name
OS Version
App Version

52. API DESIGN TIPS
Provide News alerts
Enforce Minimum App Version
"Please update
to 1.2 for improved
functionality"

53. API DESIGN TIPS
Support E-Tags and/or If-Modified-Since
Header
Provide date & paging filters on large data
sets

54. API DESIGN TIPS
Techniques for permeating deletes
Client supplies list of ids, server returns list
of valid ones
Client requests changes, server returns a set
of new records, changed records, and
deleted record ids (requires server to
support soft-delete of archive tables)

55. API DESIGN TIPS
Aggressively cache (where possible) public
endpoints
Avoid caching per-user information unless
you have a limited set of users (or unlimited
memory on your server)

56. Questions?