Developing iOS REST Applications

Luis ReiLuisRei.com

[email protected]@lmrei

DevelopingiOS

RESTApplications

• WHOAMI

• GLAZEDSOLUTIONS.COM

• HTML5 Mobile Apps - Friday 15h Main Stage

• It’s awesome: iPhone, iPad, iPod Touch

• Best Mobile App Dev Platform (by light years)

• Objective-C + Foundation + Cocoa

• Lots of potential users

• lots of potentially paying users

Why iOS

• Software architecture for distributed systems

• say web services/APIs

• Client-Server

• Works over HTTP & URI-based

• http://api.twitter.com/1/statuses/public_timeline.json

REST Quick Intro

• There’s always something you need in “the cloud”

• Data or processing power

• More true on mobile

• Universal: mobile, desktop, web clients

• It’s easy to implement server side ( at least the basic stuff)

• and everyone is doing it (twitter, github, amazon, google, ...)

• It’s easy to implement on the client

Why REST

REST/REST-Like APIs

iOS REST RecipeFunction Library I Use Currently iOS Boilerplate

HTTP Requests ASIHTTPRequest AFNetworking

JSON SBJson(AKA json-framework) JSONkit

Image Caching AFNetworking(I previously used HJCache) AFNetworking

Pull-To-Refresh PullToRefreshTableViewControllerby Leah Culver EGOTableViewPullToRefresh

HUD SVProgessHUD(I previously used DSActivityView) SVProgessHUD

• Am I connected to the internet?

• Wifi or Cellular?

Reachability(SystemConfiguration framework)

NSString * const SRVR = @"api.example.com";

-(BOOL)reachable{    Reachability *r = [Reachability reachabilityWithHostName:SRVR];

    NetworkStatus internetStatus = [r currentReachabilityStatus];

    if(internetStatus == NotReachable) {        return NO;    }    return YES;}

NotReachableReachableViaWifi

ReachableViaWWAN

GET- (void)makeGetRequest{ NSURL *url = [NSURL URLWithString:@"http://api.example.com"];

ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];

[request startSynchronous];

NSError *error = [request error];

if (!error && [request responseStatusCode] == 200){

NSString *response = [request responseString];

//NSData *responseData = [request responseData]; }

Errors

else if(error)NSLog(@"request error: %@",[error localizedDescription]);

else if([request responseStatusCode] != 200)NSLog(@"server says: %@", [request responseString]);

}

•The app continues to execute

•UI continues to be responsive

•The request runs in the background

•Two (common) ways of doing it in iOS:

•Delegate

•Block

Asynchronous Requests

• The delegator object has a delegate property that points to the delegate object

• A delegate acts when its delegator encounters a certain event

• The delegate adopts a protocol

• We’ll need 2 methods: success & failure

Cocoa Delegate Pattern

Asynchronous GET- (void)makeGetRequest{NSURL *url = [NSURL URLWithString:@"http://allseeing-i.com"];

ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url]; [request setDelegate:self];

[request startAsynchronous];}

// DELEGATE METHODS:- (void)requestFinished:(ASIHTTPRequest *)request{ NSString *responseString = [request responseString];}

- (void)requestFailed:(ASIHTTPRequest *)request{ NSError *error = [request error];}

Cocoa Blocks

• Ad hoc function body as an expression

• Carry their code & the data they need

• ideal for callbacks

• We’ll need 2 blocks: success & failure

Building Blocks- (void)makeGetRequest{ NSURL *url = [NSURL URLWithString:@"http://api.example.com"];

__block ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];

[request setCompletionBlock:^{ NSString *responseString = [request responseString]; }];

[request setFailedBlock:^{ NSError *error = [request error]; }];

[request startAsynchronous];}

SVProgressHUD

#import "SVProgressHUD.h"

- (void)makeGetRequest{ NSURL *url = [NSURL URLWithString:@"http://api.example.com"]; ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];

[SVProgressHUD showWithStatus:@"Fetching data"]; [request startSynchronous];

if (![request error]) {" [SVProgressHUD dismissWithSuccess:@"Fetch Successful"]; ... } else {" [SVProgressHUD dismissWithError:@"Fetch Failed"];

... }}

Where to Load Data• viewDidLoad / viewWillAppear

• Make the asynchronous request

• Show HUD or other “loading” indicators

• LOADED = NO;

• Delegate

• LOADED = YES;

• Reload table

• Partial Load + Pagination

• Load more at the end of the table

PullToRefresh

#import "PullRefreshTableViewController.h"

@interface MyTableViewController : PullRefreshTableViewController

- (void)refresh {  [self performSelector:@selector(add) withObject:nil afterDelay:2.0];}

- (void) add {...[self stopLoading];

}

.m

.h

Background Loading & Caching Images

#import "UIImageView+AFNetworking.h"

NSURL *imageURL = [NSURL URLWithString:@”http://example.com/picture.jpg”];UIImageView *image = [[UIImageView alloc] init];

[image setImageWithURL:imageURL];

Updating My Profile Picture

•Modify an existing record

•Authenticate

•Upload a file

ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];

[request setRequestMethod:@"PUT"]; //REST modify using PUT

[request setPostFormat:ASIMultipartFormDataPostFormat];

// authentication[request setUsername:username];[request setPassword:password];

[request setFile:jpgPath forKey:@"image"];"

[request startSynchronous];

POST & DELETE

[request setRequestMethod:@"POST"];

[request setRequestMethod:@"DELETE"];

I JSON (because it’s not XML)

JSON OBJECTIVE-C/FOUNDATION

Object NSDictionary

Array NSArray

String NSString

Number NSNumber

Boolean NSNumber (0 or 1)

1. Download a JSON string (via an http request)

2.Convert it to native data structures (parsing)

3.Use the native data structures

Parsing

[request startSynchronous];...SBJsonParser *prsr = [[[SBJsonParser alloc] init] autorelease];

// objectNSDictionary *data = [prsr objectWithString:[request responseString]];

// or ArrayNSArray *data = [parsr objectWithString:[request responseString]];

INCEPTION

[{[{}]}]An array of

objects with an array of objects

[        {                "name":  "object1",                "sub":  [                        {                                "name":  "subobject1"                        },                        {                                "name":  "subobject2"                        }                ]        },      ]

or rather JCEPTION

NSArray *jArray = [prsr objectWithString:data];

NSDictionary *obj1 = [jArray objectAtIndex:0];

NSString *obj1Name = [obj1 objectForKey:@”name”];

NSArray *obj1SubArray = [obj1 objectForKey:@”sub”];

NSDictionary *subObj1 = [obj1SubArray objectAtIndex:0];

NSNumber *subObj1Val = [subObj1 objectForKey@”value”];

[        {                "name":  "object1",                "sub":  [                        {                                "name":  "subobject1"                        },                        {                                "value":  1                        }                ]        },]

...[[[prsr objectWithSring:data] objectAtIndex:0] objectForKey:@”sub]...