iOS Web data download and JSON parsing

Introduction to iOS Web data download and JSON parsing

In this article, I will show you how to use nsurlconnection to download data from the network and how to parse the downloaded JSON data format, and how to display the data and images of the asynchronous download display

Application of the knowledge involved:

1.NSURLConnection Asynchronous Download and encapsulation

2.JSON format and JSON format parsing

3. Data display and use Sdwebimage to display images asynchronously

Content 1 Introduction to Network Download basics

What is a Web application?

In general, the vast majority of applications on the iphone require a network to operate, or network applications.

The program structure of network application

Running a program on the network to provide data to the application or to provide services, the network application is generally called the client, and the service running on the network is called the service side.

Common forms of network interfaces

Common data interfaces for iOS Web applications are usually URL addresses in the form of HTTP.

General flow of interface development

Download Data Nsurlconnection+url

Parsing Data Json/xml

Building a data Model

Creating views using view Display

TableView + Custom Cell

Picture Asynchronous Download Sdweblmage

Use of 2NSURLConnection

NSString Downloading data synchronously

　　　　

Nserror *error = nil;    Nsurl *url = [Nsurl urlwithstring:urlstring];    NSString *content = [[NSString alloc] Initwithcontentsofurl:url encoding:nsutf8stringencoding error:&error];    if (error==nil) {        NSLog (@ "content =%@", content);    }    else    {        NSLog (@ "Download Failed");    }

　　

nsurlconnection Sync Download

Nsurl *url = [Nsurl urlwithstring:urlstring];    Nsurlrequest *request = [Nsurlrequest requestwithurl:url];    Nserror *error = nil;    NSData *data = [nsurlconnection sendsynchronousrequest:request returningresponse:nil error:&error];    if (Error = = nil)    {        NSString *str = [[NSString alloc] Initwithdata:data encoding:nsutf8stringencoding];        NSLog (@ "str =%@", str);    }    else    {        NSLog (@ "Download Failed");    }

　　

Nsurlconnection Asynchronous Download

　　　　

@property (copy,nonatomic) nsmutabledata *data;//function://Incoming URL, the download completes execution after executing the target object in the action Method-(void) Requestwithurl: (    NSString *) URL target: (ID) Target action: (SEL) Action; @interface zjhttprequest () <nsurlconnectiondatadelegate>{    Nsurlconnection *_connection;    NSString *_url;    ID _target; SEL _action;}               @end @implementation zjhttprequest//function://Incoming URL, the download completes execution after executing the target object in the action Method-(void) Requestwithurl: (NSString *) URL    Target: (ID) Target action: (SEL) action{_url = URL;    _target = target;        _action = action;    Initiate URL request _data = [[Nsmutabledata alloc] init]; _connection = [[Nsurlconnection alloc] initwithrequest:[nsurlrequest requestwithurl:[nsurl URLWithString:url]] Delegate:self Startimmediately:yes];} -(void) connection: (Nsurlconnection *) connection didreceivedata: (NSData *) data{[_data appenddata:data];} -(void) connectiondidfinishloading: (nsurlconnection *) connection{//Download complete, execute Save method if (_target && [_target Res Pondstoselector:_Action]) {[_target performselector:_action withobject:self]; }    }

　　

3JSON format description and Formatting tools

　　　　

JSON format

{

"Count": 20,

"Data": [

"Zhangsan",

"Lisi",

"Wangwu"

]

}

[] represents the array, corresponding to the Nsarray

That represents the data that is tied

{} represents the dictionary, corresponding to the Nsdictionary

: represents a key-value pair

"xxx" means string, corresponding to NSString

corresponding NSNumber

Implementation of 41 completion pages (including model creation, sdwebimage use)

iOS Web data download and JSON parsing