IOS Development uses JSON to parse network data _ios

After a server request, the data returned to the client is typically in JSON format or in XML format (except for file downloads)

This article will first explain JSON parsing.

Body:

About JSON:

JSON is a lightweight data format, typically used for data interchange JSON in a format much like a dictionary and array in objective-c: {"name": "Jack", "Age": 10}

Add:

Note points in the standard JSON format: Key must be in double quotes. (But in Java it's single quotes)

Json-oc's Conversion comparison table

　　　

Wherein: null--returns the Nsnull type in OC

Use:

There are many kinds of JSON parsing schemes, but (Apple native) Nsjsonserialization performance is the best

Deserialization (JSON--> OC Object), the following example resolves to a Dictionary object

　　

Serialization (OC Object--> JSON), note that the value of the dictionary cannot be nil, but it can be passed [nsnull NULL]

　　

Not all types can be converted to JSON.

The following is an official Apple rule:

　　

Let's take another look at an example:

#import "MainViewController.h" #import "Video.h" #define Kbaseurl @ "Http://192.168.3.252/~apple" @interface Mainvi 
Ewcontroller () @property (Strong, nonatomic) Nsarray *datalist; 
@property (Weak, nonatomic) UITableView *tableview; @end @implementation mainviewcontroller class= "P1" > "412158" snippet_file_name= "blog_20140630_1_3481337" Name= "C" Ode "class=" OBJC > #pragma mark materialized View-(void) Loadview {self.view = [[UIView alloc]initwithframe:[uiscreen] Mains 
  Creen].applicationframe]; 
  1 TableView cgrect frame = self.view.bounds; UITableView *tableview = [[UITableView alloc]initwithframe:cgrectmake (0, 0, frame.size.width, frame.size.height-44) 
  Style:uitableviewstyleplain]; 
  1) data source [TableView setdatasource:self]; 
  2) Agent [TableView setdelegate:self]; 
  ) Set the table height [tableview setrowheight:80]; 
  [Self.view Addsubview:tableview]; 
   
  Self.tableview = TableView; ToolBar Uitoolbar *toolbar = [[Uitoolbar Alloc]initwithframe:cgrectmakE (0, TableView.bounds.size.height, 320, 44)]; 
   
  [Self.view Addsubview:toolbar]; Add toolbar button Uibarbuttonitem *item1 = [uibarbuttonitem alloc]initwithtitle:@ ' load json ' style: 
  Uibarbuttonitemstyledone target:self Action: @selector (Loadjson)]; Uibarbuttonitem *item2 = [[Uibarbuttonitem alloc]initwithtitle:@ ' load xml ' Style:uibarbuttonitemstyledone target:self 
  Action: @selector (Loadxml)]; Uibarbuttonitem *item3 = [[Uibarbuttonitem alloc]initwithbarbuttonsystemitem:uibarbuttonsystemitemflexiblespace 
  Target:nil Action:nil]; 
[ToolBar setitems:@[item3, Item1, Item3, ITEM2, Item3]]; 
#pragma the Mark-uitableview data source method must be implemented for UITableView the following two methods. -(Nsinteger) TableView: (UITableView *) TableView numberofrowsinsection: (nsinteger) Section {return 
Self.dataList.count; This method is called once per fill row. Know that all the rows on the interface are populated. ,-(UITableViewCell *) TableView: (UITableView *) TableView Cellforrowatindexpath: (Nsindexpath *) IndexPath {//Use of rechargeable identifiers 
  Query reusable cell static NSString *id = @ "MyCell"; UiTableviewcell *cell = [TableView dequeuereusablecellwithidentifier:id]; 
  if (cell = = nil) {cell = [[UITableViewCell alloc]initwithstyle:uitableviewcellstylesubtitle Reuseidentifier:id]; 
   
  //Set cell content Video *v = Self.datalist[indexpath.row]; 
  Cell.textLabel.text = V.name; 
  Cell.detailTextLabel.text = V.teacher; 
  Load picture//1) synchronously loads the network picture, and the synchronization method thinks that these instructions will not execute until the instruction is complete. NOTE: When developing network applications, do not use the synchronization method to load the picture, otherwise it will seriously affect the user experience//nsstring *imagepath = [NSString stringwithformat:@ "%@%@", Kbaseurl, 
V.imageurl]; 
Nsurl *imageurl = [Nsurl Urlwithstring:imagepath]; 
NSData *imagedata = [NSData Datawithcontentsofurl:imageurl]; 
UIImage *image = [UIImage imagewithdata:imagedata]; 
  //2) Asynchronously Load network picture///The network connection itself has asynchronous commands SendAsync//[Cell.imageview setimage:image]; 
    If the cached image does not exist if (v.cacheimage = = nil) {//Use the default image placeholder, you can guarantee that there is an image and there is a guarantee that there is a place. 
    UIImage *image = [uiimage imagenamed:@ "User_default.png"]; [Cell.imageview Setimage:image]; Use the default image placeholder/open asynchronous connection, plusThe image is loaded because the corresponding table needs to be refreshed after the load is complete [self loadimageasyncwithindexpath:indexpath]; 
  }else {[Cell.imageview setimage:v.cacheimage]; 
  }//[self Loadimageasyncwithurl:imageurl ImageView:cell.imageView]; 
return cell; #pragma mark asynchronously loads the network picture//Because UITableView is reusable, in order to avoid users quickly and frequently refresh the table, resulting in data conflicts, can not directly uiimageview the asynchronous method//The correct solution is to indexpath the table row 
The asynchronous method is passed in, and the specified row is refreshed directly after the finished image is loaded. 
  -(void) Loadimageasyncwithindexpath: (Nsindexpath *) Indexpath {video *v = Self.datalist[indexpath.row];//Remove the row currently being populated 
  NSString *imagepath = [NSString stringwithformat:@ "%@%@", Kbaseurl, V.imageurl]; 
   
  Nsurl *imageurl = [Nsurl Urlwithstring:imagepath]; 
  NSLog (@ "%@%@", url, ImageView); 
  1 request Nsurlrequest *request = [Nsurlrequest Requestwithurl:imageurl]; 2 Connection SendAsync asynchronous request [Nsurlconnection sendasynchronousrequest:request Queue:[nsoperationqueue MainQueue] completionhandler:^ (Nsurlresponse *response, NSData *data, Nserror *error) {//uiimage *image = [UIImage imageWithDaTa:data]; 
    [ImageView Setimage:image]; 
    Saves the network data to the cached image. 
    V.cacheimage = [UIImage imagewithdata:data]; 
  Refresh table [Self.tableview Reloadrowsatindexpaths:@[indexpath] withrowanimation:uitableviewrowanimationleft]; 
}]; 
  #pragma mark handles the JSON data-(void) Handlerjsondata: (NSData *) data {//json file, [] represents one. Deserializing JSON data//The second parameter is the parsing method, generally using nsjsonreadingallowfragments nsarray *array = [Nsjsonserialization jsonobjectwithdat 
   
  A:data options:nsjsonreadingallowfragments Error:nil]; NSLog (@ "%@", array); 
   
  JSON parsing is the data in the Nsarray format. 
  Tip: If you are developing a network application, you can save the deserialized object to the sandbox for subsequent development. 
  Nsarray *docs = Nssearchpathfordirectoriesindomains (NSDocumentDirectory, Nsuserdomainmask, YES); 
  NSString *path = [docs[0]stringbyappendingpathcomponent:@ "Json.plist"]; [Array Writetofile:path atomically:yes]; 
   
  The data inside the array is written into the jspn.plist in the sandbox. 
  Assign values to the data list nsmutablearray *arraym = [Nsmutablearray array]; For (nsdictionary *dict in array) {video *video = [VidEO alloc]init]; 
    Assign a value to a video [video setvaluesforkeyswithdictionary:dict]; 
  [Arraym Addobject:video]; 
  } self.datalist = Arraym; 
   
  Refresh table [Self.tableview Reloaddata]; NSLog (@ "%@", Arraym); This sentence will call the inside of the description and nsarray+log inside the Descriptionwithlocale} #pragma mark load JSON-(void) Loadjson {NSLog (@) 
  Load JSON "); Loading data from a Web server nsstring *str = @ "Http://www.baidu.com?format=json"; 
  Here is the Scribble//hint: NSData itself has a synchronization method, but in actual development, do not use the secondary method//When using the NSData synchronization method, can not specify the timeout, if the server connection is not normal, will affect the user experience. 
  NSData *data = [NSData datawithcontentsofurl:[nsurl urlwithstring:str]]; 
  Resume Nsurl Nsurl *url = [Nsurl urlwithstring:str]; Establish nsurlrequest nsurlrequest *request = [Nsurlrequest requestwithurl:url cachepolicy: 
  Nsurlrequestuseprotocolcachepolicy timeoutinterval:2.0f]; 
  Establish Nsurlconnect synchronization method to load data nsurlresponse *response = nil; 
  Nserror *error = nil; Synchronous load Data NSData *data = [Nsurlconnection sendsynchronousrequest:request returningresponse:&respOnse error:&error]; 
    Error-handling if (data!= nil) {//The following two sentences have no meaning in themselves and are used only for tracing debugging. 
    NSString *result = [[NSString alloc]initwithdata:data encoding:nsutf8stringencoding]; 
     
    NSLog (@ "%@", result); 
    When processing network data, do not convert NSData to NSString. 
  [Self handlerjsondata:data]; 
  }else if (data = = Nil && error = = nil) {NSLog (@ "null"); 
  }else {NSLog (@ "%@", error.localizeddescription); 
#pragma mark loads XML-(void) Loadxml {NSLog (@ "load xml"); 
}//-(void) viewdidload//{//[Super Viewdidload]; } @end