iPhone - Call a php page asynchronously and be sure it has been loaded

Question

In one of my apps, I\'d like to call asynchronously a php page I have written (http://serveradress/page.php?date=20111231), and I would be sure to know if the page could be call

Answer 1

NSURLConection is very good solution for asynchronous loading. There are few steps for creating one.

1. Setup your NSURLConnection

- (void)viewDidLoad {
    // your code...
    responseData = [[NSMutableData alloc] init];
    NSURL *url = [NSURL URLWithString:@"http://yourdomain.com/"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self]];
}

responseData is your NSMutableData iVar.

2. Implement delegate methods

a) In this method we will check for HTTP status codes

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    if ([response respondsToSelector:@selector(statusCode)]) {
        int statusCode = [((NSHTTPURLResponse *)response) statusCode];
        if (statusCode >= 400) {
            [connection cancel]; 
            NSDictionary *errorInfo = [NSDictionary dictionaryWithObject:[NSString stringWithFormat:NSLocalizedString(@"Server returned status code %d",@""),statusCode] forKey:NSLocalizedDescriptionKey];
            NSError *statusError = [NSError errorWithDomain:NSHTTPPropertyStatusCodeKey code:statusCode userInfo:errorInfo];
           [self connection:connection didFailWithError:statusError];
        }
    }
}

b) This creates your NSData component

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [responseData appendData:data];
}

c) Handles successful url connection

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    // do whatever you want using responseData as your server output
}

d) Handles errors

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    // handle your error
}

You can get error info using [error userInfo] And display it in UIAlertView, for example.

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So as I said NSURLConnection is very good solution, but you should also look at ASIHTTPRequest library. :)