How to work Synchronous and Asynchronous web in obj c [closed] - objective-c

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I'm new for development learning to parsing the data and how to work with synchronous and asynchronous requests.
NSString *url=#"http://content.guardianapis.com/search?api-key=test";
NSURLRequest *request=[NSURLRequest requestWithURL:[NSURL URLWithString:url]];
NSError *error=nil;
NSURLResponse *response;
NSData *content=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSString *string=[[NSString alloc]initWithData:content encoding:NSUTF8StringEncoding];
NSLog(#"response %#",string);
I receive a warning at the sendSynchronousRequest line. How do I process this asynchronously web request and get the response data. Explain difference of both.

Answer 1

Two separate issues here.
First, the request should be asynchronous and use NSURLSession. For example:
NSURL *url = [NSURL URLWithString:#"http://content.guardianapis.com/search?api-key=test"];
NSURLSessionTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
if (error) {
NSLog(#"%#", error);
return;
}
NSError *parseError;
NSDictionary *responseObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
if (responseObject) {
NSLog(#"%#", responseObject);
dispatch_async(dispatch_get_main_queue(), {
// if you want to update your UI or any model objects,
// do that here, dispatched back to the main queue.
});
} else {
NSString *string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"problem parsing response, it was:\n%#", string);
}
}];
[task resume];
// but do not try to use `data` here, as the above runs asynchronously
// do everything contingent upon this request _inside_ the completion
// handler above
Note, when you get the JSON response, you can parse that with NSJSONSerialization, as shown above.
Nowadays, using http for requests is frowned upon because it's not secure. You generally should use https. And NSURLSession will enforce this, returning an error if you try to use http. But if you want to force it to permit an insecure http request, you have to update your info.plist with an entry that looks like:
<key>NSAppTransportSecurity</key>
<dict>
<key>NSExceptionDomains</key>
<dict>
<key>guardianapis.com</key>
<dict>
<!--Include to allow subdomains-->
<key>NSIncludesSubdomains</key>
<true/>
<!--Include to allow HTTP requests-->
<key>NSTemporaryExceptionAllowsInsecureHTTPLoads</key>
<true/>
<!--Include to specify minimum TLS version-->
<key>NSTemporaryExceptionMinimumTLSVersion</key>
<string>TLSv1.1</string>
</dict>
</dict>
</dict>
So, go to your info.plist, control-click on it and choose "Open As" ... "Source Code" and then add the above into it. See https://stackoverflow.com/a/31254874/1271826 for more information.