This document discusses using iOS apps as clients for ERREST servers. It provides an example architecture of an iOS app connecting to an ERREST backend using REST calls. It also includes code snippets showing how to make REST requests using classes like PLRestful and CometAPI that handle the network requests and JSON parsing. The document is intended to explain how to build iOS clients for existing ERREST backends rather than how to code the iOS apps themselves.

1. iOS for ERREST
Paul Lynch
@pauldlynch
paul@plsys.co.uk

2. • We know WebObjects & ERREST
• The client problem
• Example ERREST/iOS architecture
• Some code specifics
• Some iOS client-server tips
• NOT how to write an iOS app - NO UITableView, etc
iOS for ERREST

3. App Store
• Huddle
• b-london
• iWycombe
• SOE Status
• Comet
• Mobile Adventure Walks

4. Enterprise
• DeLaRue
• Oetker
• Dorchester
• LifeFitness
• BidPresentation x 5

5. WebObjects
• Powerful system for server based development
• ERREST for RESTful servers
• Historically has used browsers for clients

6. Problem?

7. The Client
• HTML
• BUT <table>, Browser Wars, CSS
• Java Client
• BUT - Java - in the client
• Javascript/Single Page Applications
• BUT Javascript?, what framework?

8. The Client
• iOS
• iPhone for mass distribution
• iPad for Enterprise
• Objective C
• Xcode
• Foundation, UIKit

9. iOS Statistics (WWDC 2013)
• 600 million units sold
• iPad has 82% tablet market share
• iOS 6 is on 93% of all iOS devices

10. Objective C
• ARC
• properties
• blocks
• Grand Central Dispatch
• Xcode
• git
• OSS

11. • Huddle
• SaaS,Windows/IE oriented
• Comet *
• High street large enterprise, high volume shopping, ERREST
• Walks *
• “exergaming”, ERREST,Amazon EC2
• SOE Status
• game server updates
Examples

12. Comet Architecture
Marketing
db
Reviews
WO db
XML
Linux, mySQL
Change
Report
Mobile
clients

13. Comet Database
Features: skunum, runId; xml/json held as strings
Category
SKU
Review WC7SKU
Client

14. REST API
• category - parent, children
• sku
• skudetail - contains full review and XML text
• brand - attribute of sku

15. Code Approaches
• CometAPI subclasses PLRestful
• per entity subclass (Sku, Category, etc)
• NSURLConnection
• ASIHTTPRequest (not maintained)
• AFNetworking (github)
• RESTKit - RestKit.org

16. PLRestful.h
@class PLRestful;
typedef void (^PLRestfulAPICompletionBlock)(PLRestful *api, id object, int status, NSError *error);
@interface PLRestful : NSObject
@property (nonatomic, copy) NSString *endpoint;
@property (nonatomic, copy) PLRestfulAPICompletionBlock completionBlock;
@property (nonatomic, copy) NSString *username;
@property (nonatomic, copy) NSString *password;
+ (NSString *)messageForStatus:(int)status;
+ (BOOL)checkReachability:(NSURL *)url;
+ (void)get:(NSString *)requestPath parameters:(NSDictionary *)parameters completionBlock:(PLRestfulAPICompletionBlock)completion;
+ (void)post:(NSString *)requestPath content:(NSDictionary *)content completionBlock:(PLRestfulAPICompletionBlock)completion;
- (void)get:(NSString *)requestPath parameters:(NSDictionary *)parameters completionBlock:(PLRestfulAPICompletionBlock)completion;
- (void)post:(NSString *)requestPath content:(NSDictionary *)content completionBlock:(PLRestfulAPICompletionBlock)completion;
@end

17. [skudetail viewDidLoad];
NSString *query = [NSString stringWithFormat:@"skudetail/%@.json", [sku valueForKey:@"skuNum"]];
[CometAPI get:query parameters:nil completionBlock:^(CometAPI *api, id object, int status, NSError *error) {
if (error) {
[PRPAlertView showWithTitle:@"Error" message:@"Unable to fetch product details" buttonTitle:@"Continue"];
} else {
self.sku = object;
[self.tableView reloadData];
}
}];

18. CometAPI get
- (void)get:(NSString *)requestString parameters:(NSDictionary *)parameters completionBlock:(CometAPICompletionBlock)completion {
NSURL *requestURL = [[NSURL URLWithString:endpoint] urlByAddingPath:requestString andParameters:parameters];
NSLog(@"get: '%@'", [requestURL absoluteString]);
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:requestURL];
if (userName && password && useBasicAuthentication) {
NSString *authString = [[NSString stringWithFormat:@"%@:%@", userName, password] base64];
NSString *authHeader = [NSString stringWithFormat:@"Basic %@", authString];
[request setValue:authHeader forHTTPHeaderField:@"Authorization"];! !
}
//[request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
! [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
...

19. CometAPI get
...
self.completionBlock = completion;
[[UIApplication sharedApplication] prp_pushNetworkActivity];
self.restQueue = [[NSOperationQueue alloc] init];
self.restQueue.name = @"Comet REST Queue";
[NSURLConnection sendAsynchronousRequest:request queue:self.restQueue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){
if (error) {
NSLog(@"%s %@", __PRETTY_FUNCTION__, error);
[self callCompletionBlockWithObject:nil error:error];
} else {
if ([data length] == 0) {
NSLog(@"no data");
[self callCompletionBlockWithObject:nil error:[NSError errorWithDomain:@"com.plsys.semaphore.CometAPI" code:1001 userInfo:nil]];
} else {
NSError *error;
id object = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
if (object) {
[self callCompletionBlockWithObject:object error:nil];
} else {
NSLog(@"received bad json: (%d) '%@'", [data length], [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
[self callCompletionBlockWithObject:nil error:[NSError errorWithDomain:@"com.plsys.semaphore.CometAPI" code:1002 userInfo:nil]];
}
}
}
}];
}

20. CometAPI Methods
- (void)callCompletionBlockWithObject:(id)object error:(NSError *)error {
dispatch_async(dispatch_get_main_queue(), ^{
[[UIApplication sharedApplication] prp_popNetworkActivity];
self.completionBlock(self, object, error);
});
}

21. CometAPI Methods
- (NSURL *)urlByAddingPath:(NSString *)path andParameters:(NSDictionary *)parameters; {
NSString *requestString = [[self absoluteString] stringByAppendingPathComponent:path];
if (parameters) {
requestString = [requestString stringByAppendingString:@"?"];
BOOL first = YES;
for (NSString *key in [parameters allKeys]) {
if (!first) {
requestString = [requestString stringByAppendingString:@"&"];
}
requestString = [requestString stringByAppendingString:[NSString stringWithFormat:@"%@=%@", key, [[[parameters
objectForKey:key] description] stringByAddingPercentEscapesUsingEncoding:kCFStringEncodingUTF8]]];
first = NO;
}
}
return [NSURL URLWithString:requestString];
}

22. Traps
• Connection reliability
• isn’t really “always on”
• Data cacheing
• performance?
• capacity?
• Update cacheing
• Reachability

23. Write more apps!

24. Q&A
Paul Lynch
paul@plsys.co.uk
@pauldlynch