Load Web-Content Asynchronously - iphone

Question

I am trying to load web content asynchronously. I have a large amount of web calls in my viewdidappear method and my app is very unresponsive. I understand the concepts of synchronous and asynchronous loading of content, but don't know how to tell if this is being done asynchronously. The code below is simply embedded in my viewdidappear method, and I assume it is loading synchronously. How would I edit this to make it load asynchronously? Thank you all!
NSString *strURLtwo = [NSString stringWithFormat:#"http://website.com/json.php?
id=%#&lat1=%#&lon1=%#",id, lat, lon];
NSData *dataURLtwo = [NSData dataWithContentsOfURL:[NSURL URLWithString:strURLtwo]];
NSArray *readJsonArray = [NSJSONSerialization JSONObjectWithData:dataURLtwo options:0
error:nil];
NSDictionary *element1 = [readJsonArray objectAtIndex:0];
NSString *name = [element1 objectForKey:#"name"];
NSString *address = [element1 objectForKey:#"address"];
NSString *phone = [element1 objectForKey:#"phone"];

Answer 1

You can use NSURLConnectionDelegate:
// Your public fetch method
-(void)fetchData
{
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:#"http://website.com/json.php?id=%#&lat1=%#&lon1=%#",id, lat, lon]];
// Put that URL into an NSURLRequest
NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url];
// Create a connection that will exchange this request for data from the URL
connection = [[NSURLConnection alloc] initWithRequest:req
delegate:self
startImmediately:YES];
}
Implement the delegate methods:
- (void)connection:(NSURLConnection *)conn didReceiveData:(NSData *)data
{
// Add the incoming chunk of data to the container we are keeping
// The data always comes in the correct order
[jsonData appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)conn
{
// All data is downloaded. Do your stuff with the data
NSArray *readJsonArray = [NSJSONSerialization jsonData options:0 error:nil];
NSDictionary *element1 = [readJsonArray objectAtIndex:0];
NSString *name = [element1 objectForKey:#"name"];
NSString *address = [element1 objectForKey:#"address"];
NSString *phone = [element1 objectForKey:#"phone"];
jsonData = nil;
connection = nil;
}
// Show AlertView if error
- (void)connection:(NSURLConnection *)conn didFailWithError:(NSError *)error
{
connection = nil;
jsonData = nil;
NSString *errorString = [NSString stringWithFormat:#"Fetch failed: %#", [error localizedDescription]];
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:#"Error" message:errorString delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil, nil];
[alertView show];
}

Answer 2

For asynchronous web content loading, I recommend you to use AFNetworking . It'll solve lots of your major headache of networking in future. How to do:
1) subclass AFHTTPCLient, for example:
//WebClientHelper.h
#import "AFHTTPClient.h"
#interface WebClientHelper : AFHTTPClient{
}
+(WebClientHelper *)sharedClient;
#end
//WebClientHelper.m
#import "WebClientHelper.h"
#import "AFHTTPRequestOperation.h"
NSString *const gWebBaseURL = #"http://whateverBaseURL.com/";
#implementation WebClientHelper
+(WebClientHelper *)sharedClient
{
static WebClientHelper * _sharedClient = nil;
static dispatch_once_t oncePredicate;
dispatch_once(&oncePredicate, ^{
_sharedClient = [[self alloc] initWithBaseURL:[NSURL URLWithString:gWebBaseURL]];
});
return _sharedClient;
}
- (id)initWithBaseURL:(NSURL *)url
{
self = [super initWithBaseURL:url];
if (!self) {
return nil;
}
[self registerHTTPOperationClass:[AFHTTPRequestOperation class]];
return self;
}
#end
2) Request asynchronously your web content, put this code in any relevant part
NSString *testNewsURL = #"http://whatever.com";
NSURL *url = [NSURL URLWithString:testNewsURL];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFHTTPRequestOperation *operationHttp =
[[WebClientHelper sharedClient] HTTPRequestOperationWithRequest:request success:^(AFHTTPRequestOperation *operation, id responseObject)
{
NSString *szResponse = [[[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding] autorelease];
NSLog(#"Response: %#", szResponse );
//PUT your code here
}
failure:^(AFHTTPRequestOperation *operation, NSError *error)
{
NSLog(#"Operation Error: %#", error.localizedDescription);
}];
[[WebClientHelper sharedClient] enqueueHTTPRequestOperation:operationHttp];