IPhone uses http to download files and protocol usage

ArticleThere is a demo below. As I have just been familiar with the iPhone, I have learned a few things, and I would like to ask you for advice if there are any errors or deficiencies. Thank you.
Some of this ArticleCodeIt is crawling on the Internet. Refer to the article.
Http://blog.sina.com.cn/s/blog_5ccfd2d50100u04g.html iPhone file read/write operations
Http://blog.csdn.net/rhljiayou/article/details/7616365Download iPhone HTTP files

Now, let's start the journey of this article.
1. Create a new protocol file named showmsgprotocol. h.

1 # Import<Foundation/Foundation. h>2 3 @ ProtocolShowmsgprotocol <nsobject>4 5-(Void) Showmsg :( nsstring *) MSG;6 7 @ End
 

2. Add an httpdownhelper class.
First look at httpdownhelper. h file

 1   # Import <Uikit/uikit. h> 2   # Import <Foundation/Foundation. h>3   # Import   "  Showmsgprotocol. h  "  4   @ Interface  Httpdownhelper: nsobject  5   {  6       //  URL  7 Nsstring * Urlstring;  8       // Down data  9 Nsmutabledata * Datanote;  10 Nsobject <showmsgprotocol> * Showmsgdelegate;  11   }  12   13 @ Property (nonatomic, retain) nsobject <showmsgprotocol> * Showmsgdelegate;  14 @ Property (nonatomic, retain) nsstring * Urlstring;  15 @ Property (nonatomic, retain) nsmutabledata * Datanote;  16   17 -( Void ) Dodownfile :( nsstring * ) Filename;  18   19   @ End 

Check the httpdownhelper. M file.

 1   # Import   "  Httpdownhelper. h  "  2   3  @ Implementation  Httpdownhelper  4   5   @ Synthesize  Urlstring, datanote;  6   @ Synthesize  Showmsgdelegate;  7   8 -( Void ) Dodownfile :( nsstring * ) Filename {  9       10 Urlstring =[[Nsstring alloc] init];  11 Datanote = [[Nsmutabledata alloc] init];  12 Urlstring = @"  Http: // 120.172.58.15: 80/test.txt  "  ;  13 Nslog ( @"  % @  "  , Urlstring );  14 Nsurl * url =[Nsurl urlwithstring: urlstring];  15 Nsurlrequest * request = [[Nsurlrequest alloc] initwithurl: url];  16 Nsurlconnection * connect = [[nsurlconnection alloc] initwithrequest: Request Delegate  : Self];  17   [Connect release];  18   [Request release];  19   20   } 21   22   //  Accept data  23 -( Void ) Connection :( nsurlconnection *) connection didreceivedata :( nsdata * ) Data {  24   [Self. datanote appenddata: Data];  25   }  26    27    //  Data accepted  28 -( Void ) Connectiondidfinishloading :( nsurlconnection * ) Connection {  29        //  Obtain path  30        //  Which path does the nsdocumentdirectory parameter obtain?  31 Nsarray * paths = Nssearchpathfordirectoriesindomains (nsdocumentdirectory, nsuserdomainmask, yes );  32        //  Remove the required path  33 Nsstring * documentdirectory = [paths objectatindex: 0  ];  34        //  Change to the directory with the operation  35 Nsstring * Path = [documentdirectory stringbyappendingpathcomponent: @"  Test.txt  "  ];  36 Nslog ( @"  Path =% @  " , PATH );  37        38        39 Nslog ( @"  Datanote: % @  "  , [[Nsstring alloc] initwithdata: datanote encoding: nsutf8stringencoding]);  40        41   [[Nsfilemanager defaultmanager] createfileatpath: path contents: datanote attributes: Nil];  42        //  Write the downloaded data to a file. 43   [Datanote writetofile: path atomically: Yes];  44        45 Nsdata * reader = [Nsdata datawithcontentsoffile: path];  46        47 Nslog ( @"  Length = % d  "  , [READER length]);  48        49        //  Read the content of the file just written 50 Nsstring * gdata2 = [[nsstring alloc] initwithdata: [READER subdatawithrange: nsmakerange ( 0  , [READER length])] encoding: nsutf8stringencoding];  51                 52 Nslog ( @"  Gdata2 ==% @  "  , Gdata2 );  53   [Showmsgdelegate showmsg: gdata2]; // Call Protocol  54       // Lbltext. Text = gdata2;  55        56   }  57    58 -( Void ) Connection :( nsurlconnection *) connection didfailwitherror :( nserror * ) Error {  59 Uialertview * erroralert = [[uialertview alloc] initwithtitle: [error localizeddescription] Message: [error localizedfailurereason] Delegate : Nil cancelbuttontitle: @"  OK "  Otherbuttontitles: nil, nil];  60   [Erroralert show];  61   [Error release];  62   }  63   @ End 

3. Call secondviewcontroller. H on the interface.

  1  # import  
  
    2  
   # import  
   "  
    showmsgprotocol. h  
    " 
    3  
   #import  
   "  
    httpdownhelper. h  
    " 
    4  
    5  
    @ interface  secondviewcontroller: uiviewcontroller 
    
     6 -(ibaction) btndown :( 
     id  
    ) sender;  
     7  
     8  
     @ end  
   
  

Secondviewcontroller. m

 # Import   "  Secondviewcontroller. h  "  @ Interface  Secondviewcontroller ()  @ End  @ Implementation  Secondviewcontroller -( Void ) Showmsg :( nsstring * ) MSG {nslog (  @"  Showmsg =% @  " , MSG );} -(Ibaction) btndown :( ID  ) Sender {httpdownhelper * Httphepler = [[Httpdownhelper alloc] init]; [httphelper dodownfile:  @"  Test.txt  "  ];
Httphelper.Showmsgdelegate = self;}
@ End 

OK,Demo download: Httpdowndemo