Posting data to url in Objective-C

Copy from: http://panditpakhurde.wordpress.com/2009/04/16/posting-data-to-url-in-objective-c/
 
Here, I am leaving some important notes that you can use in your code for sending data for login page link or a particular forum link using objective C. Also you can use this for posting comments or posting posts to a particular forum or url link.
I am mentioning all the relative apis with the dummy urls for your understanding the whole procedure. Follow the points as per mentioned below

For sake of understanding , take an example of sending username and password to your login page. To do this follow the following steps.

1. set post string with actual username and password.

NSString *post = [NSString stringWithFormat:@"&Username=%@&Password=%@",@"username",@"password"];

2. Encode the post string using NSASCIIStringEncoding and also the post string you need to send in NSData format.

NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];

You need to send the actual length of your data. Calculate the length of the post string.

NSString *postLength = [NSString stringWithFormat:@"%d",[postData length]];

3. Create a Urlrequest with all the properties like HTTP method, http header field with length of the post string.
Create URLRequest object and initialize it.

NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease];

Set the Url for which your going to send the data to that request.

[request setURL:[NSURL URLWithString:[NSString stringWithFormat:@"http://www.abcde.com/xyz/login.aspx"]]];

Now, set HTTP method (POST or GET).
Write this lines as it is in your code.

[request setHTTPMethod:@"POST"];

Set HTTP header field with length of the post data.

[request setValue:postLength forHTTPHeaderField:@"Content-Length"];

Also set the Encoded value for HTTP header Field.

[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Current-Type"];

Set the HTTPBody of the urlrequest with postData.

[request setHTTPBody:postData];

4. Now, create URLConnection object. Initialize it with the URLRequest.

NSURLConnection *conn = [[NSURLConnection alloc]initWithRequest:request delegate:self];

It returns the initialized url connection and begins to load the data for the url request. You can check that whether you URL connection is done properly or not using just if/else statement as below.

if(conn)
{
NSLog(@”Connection Successful”)
}
else
{
NSLog(@”Connection could not be made”);
}

5. To receive the data from the HTTP request , you can use the delegate methods provided by the URLConnection Class Reference. Delegate methods are as below.

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData*)data

Above method is used to receive the data which we get using post method.

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error

This method , you can use to receive the error report in case of connection is not made to server.

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

The above method is used to process the data after connection has made successfully.


Have a Happy Coding !