Hypermedia for the iOS developer - Swipe 2012

PlayUp Pty Ltd

Kevin O’Neill

Network Connectedhypermedia for the iOS developer

SWIPE CONFERENCE 2012

Roadmap

• Some background

• Introduction to hypermedia

• Consuming a hypermedia API

• Bit’s and Pieces


CTO PlayUp


Blood


This will be an introduction


Opinionated


ReST



It’s been mutated to the point of being meaningless


CRUD = ReST


URL Patterns = REST


http://example.com/products/<id>

http://example.com/products/1

http://example.com/products/1


Well No


Hypermedia API’s


The Good


Loose Coupling


Simplicity / Uniformity


Scale better


The Bad


Not the most succinct form


Cache invalidation is hard


It takes more thought


What is a hypermedia API


Use HTTP Properly*


Use links to guide clients through processes


"REST is software design on the scale of decades: every detail is intended to promote software longevity and independent evolution.

Many of the constraints are directly opposed to short-term ef!ciency. Unfortunately, people are

fairly good at short-term design, and usually awful at long-term design." - Roy Fielding


Consuming a Hypermedia API


{ "title": "Raiders vs Bulldogs", "short_title": "RAI vs BUL",

"scheduled_start_time": "2012-‐08-‐24T09:35:00Z", "start_time": "2012-‐08-‐24T09:35:00Z", "end_time": "2012-‐08-‐24T12:24:54Z", "clock": { "summary": "2ND 61:56", "minutes": 61, "seconds": 56, "period": 2 },

...


Content-‐Type


Content-‐Type

application/json


Content-‐Type

application/vnd.example.contest.rugby_league+json


Strategy


@protocol HTTPResponseHandler <NSObject>

-‐ (void)handle:(NSHTTPURLResponse *)response forRequest:(id <RequestToken>)request;

@end

@interface RegistryHandler : NSObject <HTTPResponseHandler>

-‐ (void)registerHandler:(id<HTTPResponseHandler>)handler for:(id<TypeMatcher>)matcher;

@end


Errors


"scores": [ { "total": 34, "summary": "34", "team": { ":href": "http://example.com/teams/569", ":type": "application/vnd.example.sport.team+json" ":links" [ { "rel": "alternate", "href": "http://example.com/teams/569.xml" "type": "application/vnd.example.sport.team+xml" }, { "rel": "alternate", "href": "http://example.com/teams/569.html" "type": "text/html" }

http://example.com/sportsdata/teams/569


http://example.com/sportsdata/teams/569.xml


http://example.com/sportsdata/teams/569.html



"scores": [ { "total": 34, "summary": "34", "team": { ":href": "http://example.com/teams/569", ":type": "application/vnd.example.sport.team+json" ":links" [ { "rel": "alternate", "href": "http://example.com/teams/569.xml" "type": "application/vnd.example.sport.team+xml" }, { "rel": "alternate", "href": "http://example.com/teams/569.html" "type": "text/html" }








"scores": [ { "total": 34, "summary": "34", "team": { ":href": "http://example.co/t/d/dogs.json", ":type": "application/vnd.example.sport.team+json", ":links" [ { "rel": "alternate", "href": "http://example.com/teams/569.xml" "type": "application/vnd.example.sport.team+xml" }, { "rel": "alternate", "href": "http://example.com/teams/569.html" "type": "text/html" }








Versioning and Alternates


"scores": [ { "total": 34, "summary": "34", "team": { ":href": "http://example.com/teams/569", ":type": "application/vnd.example.sport.team+json", ":links" [ { "rel": "alternate", "href": "http://example.com/teams/569.xml" "type": "application/vnd.example.sport.team+xml" }, { "rel": "alternate", "href": "http://example.com/teams/569.html" "type": "text/html" }








Accept

application/vnd.example.sport.team+xml


Accept

application/vnd.example.sport.team+xml,*/*


"scores": [ { "total": 34, "summary": "34", "team": { ":href": "http://example.com/teams/569", ":type": "application/vnd.example.sport.team+json", ":links" [ { "rel": "alternate", "href": "http://example.com/teams/569.xml" "type": "application/vnd.example.sport.team+xml" }, { "rel": "alternate", "href": "http://example.com/teams/569.html" "type": "text/html" }








NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url]; [request setHTTPMethod:@"GET"]; [request addValue:@"text/html,*/*" forHTTPHeaderField:@"Accept"];


Caching


NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:kMemoryCacheSize diskCapacity:kDiskCacheSize diskPath:cache_path]; [NSURLCache setSharedURLCache:sharedCache];


ETag"9461cf5ecc0f4df6e880ce76479aba90"

Cache-‐Controlmax-‐age=15, public

VaryAccept-‐Language


NSMutableURLRequest *request = ...

[request setValue:etag forHTTPHeaderField:@"If-‐None-‐Match"];


NSMutableURLRequest *request = ...

[request setValue:etag forHTTPHeaderField:@"If-‐None-‐Match"];

[request setCachePolicy: NSURLRequestReloadIgnoringLocalCacheData];


static NSUInteger calc_timeout(NSHTTPURLResponse *response) { NSUInteger new_timeout = k_default_expires; NSString *cache_control = [[response allHeaderFields] valueForKey:@"Cache-‐Control"]; if (nil != cache_control) { NSRange maxage_range = [cache_control rangeOfString:@"max-‐age="]; if (maxage_range.location != NSNotFound) { NSString *timeout_str = [cache_control substringFromIndex:NSMaxRange(maxage_range)]; NSRange comma_range = [timeout_str rangeOfString:@","]; if (NSNotFound != comma_range.location) { timeout_str = [timeout_str substringToIndex:comma_range.location]; } new_timeout = (NSUInteger)[timeout_str integerValue]; } } return new_timeout;}


Bits and Pieces


Test from other countries


Charles is your friend


HTTPShouldUsePipelining


gzip encoding is your friend


Proxies Screw You


Kevin O’NeillCTO - PlayUp

[email protected]@kevinoneill

Questions

mailto:[email protected]

mailto:[email protected]

Documents

Hypermedia for the iOS developer - Swipe 2012