iOS: Web Services and XML parsing

iOS: Web Services and XML parsing

• 1.
  iOS:  Web  Services  and  XML  Parsing   Jussi  Pohjolainen   Tampere  University  of  Applied  Sciences  
• 2.
  About  Web  Services   •  Fetch  content  via  HTTP   •  Parse  the  content   •  Content  is  usually   –  XML   –  JSON   •  Example:  weather  data,  bus  traffic   informaLon,  twiMer…  
• 3.
  HTTP  GET  
• 4.
  Fetching  content  over  HTTP   •  In  iOS  it’s  easy  to  fetch  content  over  HTTP   •  Classes  needed   –  NSURL   –  NSURLRequest   –  NSURLConnecLon   •  The  NSURLConnecLon  has  a  delegate   NSURLConnecLonDelegate  which  holds   methods  like  didReceiveData  and   connecLonDidFinishLoading  
• 5.
  NSURLConnecLon  Example  
• 6.
  NSURLConnecLonDelegate  
• 7.
  PARSING  XML  
• 8.
  OpLons   •  SAX   –  Event  driven   –  Does  not  consume  lot  of  memory   –  iOS:  NSXMLParser     •  Dom   –  Reads  enLre  document  to  memory   –  You  can  move  in  the  object  tree   –  libxml2  –  C  based  API  for  SAX  and  DOM    
• 9.
  Third  Party  OpLons   •  TBXML   –  Lightweight  DOM,  read  only   •  TouchXML   –  DOM  and  XPath,  read  only   •  KissXML   –  TouchXML  +  ediLng  of  xml   •  GDataXML   –  DOM    and  Xpath,  read  and  write,  developed  by   Google  
• 10.
  NSData  vs.  NSMutableData   •  NSMutableData   –  Wrapper  for  byte  buffer.  Can  be  modified   •  NSData   –  Wrapper  for  byte  buffer.  Cannot  be  modified   •  In  didReceiveData  
• 11.
  Parsing  XML  Data  using  NSXMLParser   •  iOS  has  NSXMLParser  for  parsing  data  in  an   event  driven  way  (can  be  complicated).   •  The  NSXMLParser  opens  xml  data  and  calls   methods  like   –  didStartElement   –  foundCharacters   –  didEndElement  
• 12.
  How  to  start  parsing  XML?   The  NSXMLParserDelegate  provides  you  methods:  
• 13.
  JSON  
• 14.
  JSON   •  JavaScript  Object  NotaLon,  is  a  text-­‐based   open  standard  designed  for  human-­‐readable   data  interchange   •  RepresenLng  simple  data  structures  and   associaLve  arrays,  called  objects.   •  Despite  its  relaLonship  to  JavaScript,  it  is   language-­‐independent,  with  parsers  available   for  many  languages.  
• 15.
  Example   { "response":{ "version":"0.1", "termsofService":"http://www.wunderground.com/weather/api/d/terms.html", "features":{ "conditions":1 } }, "current_observation":{ "image":{ "url":"http://icons-ak.wxug.com/graphics/wu2/logo_130x80.png", "title":"Weather Underground", "link":"http://www.wunderground.com" }, "display_location":{ "full":"Tampere, Finland", "city":"Tampere", "state":"", "state_name":"Finland", "country":"FI", "country_iso3166":"FI", "zip":"00000", "latitude":"61.41999817", "longitude":"23.57999992",
• 16.
  JSON  Parsing   • From  iOS  5  and  above,  you  can  do  JSON   parsing  using  NSJSONSerializaLon   •  Convert  JSON  to  foundaLon  objects  and  back   •  See  Doc   –  hMp://developer.apple.com/library/ios/ #documentaLon/FoundaLon/Reference/ NSJSONSerializaLon_Class/Reference/ Reference.html  
• 17.
  Parsing   NSError* errorObject; //_data (NSData) contains parsable json content NSDictionary* json = [NSJSONSerialization JSONObjectWithData: _data options:NSJSONReadingMutableContainers error:&errorObject]; NSDictionary* observation = [json objectForKey:@"current_observation"]; NSDictionary* displayLocation = [observation objectForKey:@"display_location"]; // “Tampere” NSString* city = [[NSString alloc] initWithFormat:@"%@", [displayLocation objectForKey:@"city"]]