ITP 342 Mobile App Dev

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1 ITP 342 Mobile App Dev

2 REST Representational state transfer (REST) is a style of software architecture for distributed hypermedia systems such as the World Wide Web Conforming to the REST constraints is referred to as being RESTful RESTful web service (or RESTful web API) is a simple web service implemented using HTTP and the principles of REST It is a collection of resources with 4 defined aspects 2

3 REST Philosophy The 3 most important features of a RESTful server are its statelessness, uniform resource identification, and cacheability. Statelessness Every API is treated as a new request, and no client context is remembered on the server. Resource identification Done through URLs Cacheability Allows clients to cache responses based on the URL 3

4 REST Philosophy Response from a RESTful server is usually sent in a uniform, agreed-upon format, usually to decouple the client/server interface. The client ios app communicates with a RESTful server through this agreed-upon data exchange format. The most commonly used formats are XML and JSON. 4

5 RESTful Web Services The base URI for the web service, such as The Internet media type of the data supported by the web service Often JSON (JavaScript Object Notation), XML (Extensible Markup Language) or YAML but can be any other valid Internet media type The set of operations supported by the web service using HTTP methods (e.g., GET, PUT, POST, or DELETE) The API must be hypertext driven 5

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7 REST Services Many web sites are now offering their facilities through REST Web Services REST Services can be used to access sites that perform the following functions: Web Search (e.g.yahoo s BOSS Search, Google Custom Search) Geolocation (e.g Yahoo s Placefinder) Photo Sharing (e.g. Yahoo s Flickr, Google s Picasa) Social Networking (e.g. Facebook, Twitter, Instagram) Mapping (e.g. Google Maps) Many of these services limit daily usage by a single website, and require payment when the thresholds are breached 7

8 REST Services Access is provided using one or both of these methods: Direct URL, returning a response in one or more formats (XML, JSON, PHP) Library-based APIs, embedded in JavaScript, Java, C#, Objective-C and other source and binary library formats Many of these services now require or include OAuth user authentication Oauth is a standard for clients to access server resources on behalf of a resource owner E.g. see 8

xml version="1.0" encoding="utf-8"?>! <note>! <to>jason</to>!

9 XML XML stands for extensible Markup Language Designed to transport and store data Uses tags Has a root node <?xml version="1.0" encoding="utf-8"?>! <note>! <to>jason</to>! <from>trina</from>! <heading>reminder</heading>! <body>bring home some milk!</body>! </note>! 9

JSON JSON stands for JavaScript Object Notation Is a lightweight text-data interchange format Is "self-describing" and easy to understand http://www.w3schools.

10 JSON JSON stands for JavaScript Object Notation Is a lightweight text-data interchange format Is "self-describing" and easy to understand {! }! "employees": [! { "firstname":"trina", "lastname":"gregory" },! { "firstname":"chitvan", "lastname":"gupta" },! { "firstname":"poojan", "lastname":"jhaveri" }! ]! 10

11 Parsing XML on ios You can do XML parsing using 2 kinds of parsers: A DOM (Document Object Model) parser A SAX (Simple API for XML) parser XML Parser for ios 11

12 SAX Parser Most SAX parsers work by taking in a URL as a parameter and giving you data as it becomes available. The NSXMLParser foundation class has a method called initwithcontentsofurl:! You essentially initialize a parser object with the URL, and the NSXMLParser does the rest. Parsed data becomes available through callback via delegate methods defined in NSXMLParserDelgate. 12

13 NSXMLParser Conform to the NSXMLParserDelegate. The most commonly handled methods are: parserdidstartdocument:! parserdidenddocument:! parser: didstartelement: namespaceuir: qualifiedname: attributes:! parser: didendelement: namespaceuri: qualifiedname:! parser: foundcharacters:! 13

14 DOM Parser A DOM parser loads the complete XML before it starts parsing. The advantage of using a DOM parser is its capability to access data at random using XPath queries, and there's no delegation as in the SAX model. ios does not have an Objective-C-based DOM parser built in. You can use libxml2 or third-party wrappers such as KissXML, TouchXML, or GDataXML. 14

15 Parsing JSON on ios JSON is much more commonly used than XML. With ios 5, Apple introduced NSJSONSerialization, which is Apple's JSON parsing and serializing framework. You also can choose from plenty of thirdparty JSON processing frameworks. The most commonly used are SBJson, TouchJSON, YAJL, and JSONKit. 15

16 Important Reminders Never make a synchronous network call. Even if they're on a background thread, synchronous calls don't report progress. Another reason is that to cancel a synchronous request running on a background thread, you have to kill the thread. Avoid using NSThread or GCD-based threading directly for network operations (unless your project is small and has just a couple of API calls). Use NSOperationQueue-based threading instead. NSOperationQueue helps with controlling the queue length and the number of concurrent network operations. 16

17 NSURLConnection Apple provides classes in CFNetwork.framework and provides a Foundation-based NSURLConnection for making asynchronous requests. MKNetworkKit is a block-based wrapper around NSURLConnect that doesn't bloat your code base while providing powerful features, most importantly, caching. 17

18 Resources ios 7 Programming: Pushing the Limits by Rob Napier and Mugunth Kumar Chapter 12: REST for the Weary ios 7 Programming: Pushing the Limits by Rob Napier and Mugunth Kumar Chapter 11: Behind the Scenes: Background Processing 18

19 Network Access Common background task is making a network request We want to ensure that user data is saved to a server even if the user leaves the app in the middle of your save action In ios 6, we would wrap the network request with beginbackgroundtaskwithexpiration Handler:! Works for small requests 19

20 New Solution In ios 7, the preferred way is NSURLSession There is no simple, universal way to implement background transfers with NSURLSession Need to adapt it heavily to your specific situation NSURLSession is a replacement for NSURLConnection 20

21 NSURLSession Previously [NSURLConnection sendasynchronousrequest: queue:! completionhandler: ]! Use [NSURLSession datataskwithurl: completionhandler: ]! 21

22 NSURLSession Previously [NSURLConnection sendasynchronousrequest: request! queue: [NSOperationQueue mainqueue]! completionhandler: handler];! Use NSURLSessionTask *task = [[NSURLSession sharedsession]! datataskwithrequest: request:! completionhandler: handler];! [task resume];! 22

Session Configuration After this, you can get a few features Query the task for info such as its originalrequest and its countofbytesexpectedtorecieve You can start configuring the session You can

23 Session Configuration After this, you can get a few features Query the task for info such as its originalrequest and its countofbytesexpectedtorecieve You can start configuring the session You can configure a session that doesn't use cellular data NSURLSessionConfiguration *configuration =! [NSURLSessionConfiguration defaultsessionconfiguration];! [configuration setallowscellularaccess: NO];! NSURLSession *session = [NSURLSession! sessionwithconfiguration: configuration];! 23

24 Session Configuration NSURLSession has 3 build-in configurations: defaultsessionconfiguration! Matches the behavior of NSURLConnection Uses the shared cache, cookie storage, etc. ephemeralsessionconfiguration! Uses only in-memory storage Nothing is written to disk backgroundsessionconfiguration:! Takes an identifier and is configured to perform network transfers while your app is in the background, or even when it is terminated 24

25 ASIHTTPRequest RESTful API Easy to use wrapper around the CFNetwork API Suitable for basic HTTP requests and interacting with REST-based services Developing RESTful ios Apps with RestKit restkit_ios-sdk/ 25

26 Tutorials AppCoda Fetch and Parse JSON AppCoda XML and JSON Parsing Ray Wenderlich JSON Touch Code Fetch and Parse JSON 26

27 Frameworks AFNetworking networking framework RestKit RESTful framework introduction-restkit-tutorial 27

ITP 140 Mobile Technologies. Mobile Topics

ITP 140 Mobile Technologies. Mobile Topics ITP 140 Mobile Technologies Mobile Topics Topics Analytics APIs RESTful Facebook Twitter Google Cloud Web Hosting 2 Reach We need users! The number of users who try our apps Retention The number of users