In iOS (current target 5.0, Base SDK 5.1) how can I send a post request to a server, and then read the contents of the page. For example, the page takes a username and password, and then echos true or false. This is just for a better understanding of NSURLRequest.
Thanks in Advance!
A few things first
Aim to make all your url connections asynchronous so your UI remains responsive. You can do this with NSURLConnectionDelegate callbacks. NSURLConnection has a small drawback: your code must be decoupled. Any variables you want available in the delegate functions will need to be saved to ivars or in your request's userInfo dict.
Alternatively you can use GCD, which, when coupled with the __block qualifiers, allows you to specify error/return code at the point you declare it - useful for one off fetches.
Without further ado, here's a quick and dirty url-encoder:
- (NSData*)encodeDictionary:(NSDictionary*)dictionary {
NSMutableArray *parts = [[NSMutableArray alloc] init];
for (NSString *key in dictionary) {
NSString *encodedValue = [[dictionary objectForKey:key] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSString *encodedKey = [key stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSString *part = [NSString stringWithFormat: @"%@=%@", encodedKey, encodedValue];
[parts addObject:part];
}
NSString *encodedDictionary = [parts componentsJoinedByString:@"&"];
return [encodedDictionary dataUsingEncoding:NSUTF8StringEncoding];
}
Using a JSON library like JSONKit makes encoding things easier, consider it!
// .h
@interface ViewController : UIViewController<NSURLConnectionDelegate>
@end
// .m
@interface ViewController () {
NSMutableData *receivedData_;
}
@end
...
- (IBAction)asyncButtonPushed:(id)sender {
NSURL *url = [NSURL URLWithString:@"http://localhost/"];
NSDictionary *postDict = [NSDictionary dictionaryWithObjectsAndKeys:@"user", @"username",
@"password", @"password", nil];
NSData *postData = [self encodeDictionary:postDict];
// Create the request
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"POST"];
[request setValue:[NSString stringWithFormat:@"%d", postData.length] forHTTPHeaderField:@"Content-Length"];
[request setValue:@"application/x-www-form-urlencoded charset=utf-8" forHTTPHeaderField:@"Content-Type"];
[request setHTTPBody:postData];
NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request
delegate:self];
[connection start];
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
[receivedData_ setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[receivedData_ appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
NSLog(@"Succeeded! Received %d bytes of data", [receivedData_ length]);
NSString *responeString = [[NSString alloc] initWithData:receivedData_
encoding:NSUTF8StringEncoding];
// Assume lowercase
if ([responeString isEqualToString:@"true"]) {
// Deal with true
return;
}
// Deal with an error
}
// .m
- (IBAction)dispatchButtonPushed:(id)sender {
NSURL *url = [NSURL URLWithString:@"http://www.apple.com/"];
NSDictionary *postDict = [NSDictionary dictionaryWithObjectsAndKeys:@"user", @"username",
@"password", @"password", nil];
NSData *postData = [self encodeDictionary:postDict];
// Create the request
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"POST"];
[request setValue:[NSString stringWithFormat:@"%d", postData.length] forHTTPHeaderField:@"Content-Length"];
[request setValue:@"application/x-www-form-urlencoded charset=utf-8" forHTTPHeaderField:@"Content-Type"];
[request setHTTPBody:postData];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Peform the request
NSURLResponse *response;
NSError *error = nil;
NSData *receivedData = [NSURLConnection sendSynchronousRequest:request
returningResponse:&response
error:&error];
if (error) {
// Deal with your error
if ([response isKindOfClass:[NSHTTPURLResponse class]]) {
NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse*)response;
NSLog(@"HTTP Error: %d %@", httpResponse.statusCode, error);
return;
}
NSLog(@"Error %@", error);
return;
}
NSString *responeString = [[NSString alloc] initWithData:receivedData
encoding:NSUTF8StringEncoding];
// Assume lowercase
if ([responeString isEqualToString:@"true"]) {
// Deal with true
return;
}
// Deal with an error
// When dealing with UI updates, they must be run on the main queue, ie:
// dispatch_async(dispatch_get_main_queue(), ^(void){
//
// });
});
}
+ (void)sendAsynchronousRequest:(NSURLRequest *)request queue:(NSOperationQueue *)queue completionHandler:(void (^)(NSURLResponse*, NSData*, NSError*))handler
Hope this helps.