1. Overview 1.1 Header 2. Working with NSURLConnection 2.1 Preflighting a Connection Request 2.2 Connection URL Information 2.3 Loading Data Synchronously 2.4 Loading Data Asynchronously 2.5 Stopping a Connection 3. Working with RESTful Web Services 4. Working with JSON 4.1 What is JSON? 4.2 JSON’s basic types are: 4.3 NSJSONSerialization 5. Exercise 6

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Networking
Linh NGUYEN
Lecture 6

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Contents
2
Overview1
Working with NSURLConnection2
Working with RESTful Web Services3
Working with JSON4
Exercise 65

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Networking
Overview
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Overview
4
ServerClient
BODY + Header
BODY + Header
Request
Response

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Overview
 Header
 Field names
• http://en.wikipedia.org/wiki/List_of_HTTP_header_fields
• Additional field names and permissible values may be defined by each
application.
 Size limits
• There are no limits to the size of each header field name or value or to the
number of headers in the standard itself. However, most servers, clients, and
proxy software impose some limits for practical and security reasons. For
example, the Apache 2.3 server by default limits each header size to 8190
bytes, and there can be at most 100 headers in a single request
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Overview
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Header
Content-Length 1000
Content-Type
application/x-www-
form-urlencoded
Range bytes=500-999
User-Agent Mobile

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Overview
7
Request
POST
GET

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Networking
NSURLConnection
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NSURLConnection
 An NSURLConnection object provides support to perform
the loading of a URL request. The interface for
NSURLConnection is sparse, providing only the controls to
start and cancel asynchronous loads of a URL request.
 NSURLConnection’s delegate methods—defined by the
NSURLConnectionDelegate protocol—allow an object to
receive informational callbacks about the asynchronous load
of a URL request.
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NSURLConnection
 NSURLConnection has a convenience class method,
sendSynchronousRequest:returningResponse:error:, to
load a URL request synchronously.
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NSURLConnection
 Preflighting a Connection Request
 + canHandleRequest:
 Connection URL Information
 – originalRequest
 – currentRequest
 Loading Data Synchronously
 + sendSynchronousRequest:returningResponse:error:
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NSURLConnection
 Loading Data Asynchronously
 + connectionWithRequest:delegate:
 – initWithRequest:delegate:
 – initWithRequest:delegate:startImmediately:
 + sendAsynchronousRequest:queue:completionHandler:
 – start
 Stopping a Connection
 – cancel
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NSURLConnection
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NSURLConnection
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Networking
Working with RESTful Web Services
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Working with RESTful Web Services
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Working with RESTful Web Services
17
DELETE
Client
POST
GET
PUT
RESTful Web
services DB

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Working with RESTful Web Services
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XML
JSON
OTHER
REQUEST
or
RESPONSE
URL
HEADER
BODY

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Working with RESTful Web Services
19
XML
JSON
OTHER

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Working with RESTful Web Services
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URL
HEADER
BODY
POST
http://nikmesoft.com/steven/vietfooding/users/login.json
api_key = a30e38ce87e30dd2a6f7e858ce68dcc3
email = test02@gmail.com
password = 1

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Working with RESTful Web Services
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Working with RESTful Web Services
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URL
HEADER
GET
http://nikmesoft.com/steven/vietfooding/users/?id=1/
api_key = a30e38ce87e30dd2a6f7e858ce68dcc3

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Web services
Working with JSON
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Working with JSON
 What is JSON?
 JSON or JavaScript Object Notation, is a text-based open
standard designed for human-readable data interchange. It is
derived from the JavaScript scripting language for representing
simple data structures and associative arrays, called objects.
Despite its relationship to JavaScript, it is language-independent,
with parsers available for many languages.
 The JSON format is often used for serializing and transmitting
structured data over a network connection. It is used primarily to
transmit data between a server and web application, serving as an
alternative to XML.
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Working with JSON
 JSON’s basic types are:
 Number
 String (double-quoted Unicode, with backslash escaping)
 Boolean (true or false)
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Working with JSON
 JSON’s basic types are:
 Array (an ordered sequence of values, comma-separated and
enclosed in square brackets; the values do not need to be of the
same type)
 Object (an unordered collection of key:value pairs with the ':'
character separating the key and the value, comma-separated and
enclosed in curly braces; the keys must be strings and should be
distinct from each other)
 null (empty)
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Working with JSON
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Working with JSON
 NSJSONSerialization
 You use the NSJSONSerialization class to convert JSON to
Foundation objects and convert Foundation objects to JSON.
 An object that may be converted to JSON must have the following
properties:
• The top level object is an NSArray or NSDictionary.
• All objects are instances of NSString, NSNumber, NSArray, NSDictionary, or
NSNull.
• All dictionary keys are instances of NSString.
• Numbers are not NaN or infinity.
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Working with JSON
 NSJSONSerialization
 Other rules may apply. Calling isValidJSONObject: or attempting a
conversion are the definitive ways to tell if a given object can be
converted to JSON data.
 Creating a JSON Object
• + JSONObjectWithData:options:error:
• + JSONObjectWithStream:options:error:
 Creating JSON Data
• + dataWithJSONObject:options:error:
• + writeJSONObject:toStream:options:error:
• + isValidJSONObject:
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Working with JSON
 NSJSONSerialization
 JSONObjectWithData:options:error:
• NSJSONReadingMutableContainers
– Specifies that arrays and dictionaries are created as mutable objects.
• NSJSONReadingMutableLeaves
– Specifies that leaf strings in the JSON object graph are created as instances of NSMutableString.
• NSJSONReadingAllowFragments
– Specifies that the parser should allow top-level objects that are not an instance of NSArray or
NSDictionary.
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Exercise 6
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