NSURLConnection wrong order - ios

Question

I have a NSURLConnection (two of them), and they're running in the wrong order.
Here's my method:
- (void)loginToMistarWithPin:(NSString *)pin password:(NSString *)password {
NSURL *url = [NSURL URLWithString:#"https://mistar.oakland.k12.mi.us/novi/StudentPortal/Home/Login"];
//Create and send request
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:#"POST"];
NSString *postString = [NSString stringWithFormat:#"Pin=%#&Password=%#",
[self percentEscapeString:pin],
[self percentEscapeString:password]];
NSData * postBody = [postString dataUsingEncoding:NSUTF8StringEncoding];
[request setHTTPBody:postBody];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
// do whatever with the data...and errors
if ([data length] > 0 && error == nil) {
NSError *parseError;
NSDictionary *responseJSON = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
if (responseJSON) {
// the response was JSON and we successfully decoded it
NSLog(#"Response was = %#", responseJSON);
} else {
// the response was not JSON, so let's see what it was so we can diagnose the issue
NSString *loggedInPage = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"Response was not JSON (from login), it was = %#", loggedInPage);
}
}
else {
NSLog(#"error: %#", error);
}
}];
//Now redirect to assignments page
NSURL *homeURL = [NSURL URLWithString:#"https://mistar.oakland.k12.mi.us/novi/StudentPortal/Home/PortalMainPage"];
NSMutableURLRequest *requestHome = [[NSMutableURLRequest alloc] initWithURL:homeURL];
[request setHTTPMethod:#"POST"];
[NSURLConnection sendAsynchronousRequest:requestHome queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *homeResponse, NSData *homeData, NSError *homeError)
{
// do whatever with the data...and errors
if ([homeData length] > 0 && homeError == nil) {
NSError *parseError;
NSDictionary *responseJSON = [NSJSONSerialization JSONObjectWithData:homeData options:0 error:&parseError];
if (responseJSON) {
// the response was JSON and we successfully decoded it
NSLog(#"Response was = %#", responseJSON);
} else {
// the response was not JSON, so let's see what it was so we can diagnose the issue
NSString *homePage = [[NSString alloc] initWithData:homeData encoding:NSUTF8StringEncoding];
NSLog(#"Response was not JSON (from home), it was = %#", homePage);
}
}
else {
NSLog(#"error: %#", homeError);
}
}];
}
- (NSString *)percentEscapeString:(NSString *)string
{
NSString *result = CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
(CFStringRef)string,
(CFStringRef)#" ",
(CFStringRef)#":/?#!$&'()*+,;=",
kCFStringEncodingUTF8));
return [result stringByReplacingOccurrencesOfString:#" " withString:#"+"];
}
So, it's two NSURLConnection's that are added to the [NSOperationQueue mainQueue]. What my output is showing me is that the second NSURLConnection is running before the first one. So it tries to go to the page where I download data before I'm logged in, so it (obviously) returns a "You're not logged in" error.
How do I schedule them one after another?

Answer 1

The issue, as I suspect you have realized, is that you're doing asynchronous network requests (which is good; you don't want to block the main queue), so there's no assurance of the order they'll finish.
The quickest and easiest answer is to simply put the call to the second request inside the completion block of the first one, not after it. You don't want to be making that second one unless the first one succeeded anyway.
To keep your code from getting unwieldy, separate the login from the request for main page. And you can use the completion block pattern which is common with asynchronous methods. You add a parameter to loginToMistarWithPin that specifies what it should do when the request finishes. You might have one completion block handler for success, and one for failure:
- (void)loginToMistarWithPin:(NSString *)pin password:(NSString *)password success:(void (^)(void))successHandler failure:(void (^)(void))failureHandler {
NSURL *url = [NSURL URLWithString:#"https://mistar.oakland.k12.mi.us/novi/StudentPortal/Home/Login"];
//Create and send request
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:#"POST"];
NSString *postString = [NSString stringWithFormat:#"Pin=%#&Password=%#",
[self percentEscapeString:pin],
[self percentEscapeString:password]];
NSData * postBody = [postString dataUsingEncoding:NSUTF8StringEncoding];
[request setHTTPBody:postBody];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
// do whatever with the data...and errors
if ([data length] > 0 && error == nil) {
NSError *parseError;
NSDictionary *responseJSON = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
if (responseJSON) {
// the response was JSON and we successfully decoded it
NSLog(#"Response was = %#", responseJSON);
// assuming you validated that everything was successful, call the success block
if (successHandler)
successHandler();
} else {
// the response was not JSON, so let's see what it was so we can diagnose the issue
NSString *loggedInPage = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"Response was not JSON (from login), it was = %#", loggedInPage);
if (failureHandler)
failureHandler();
}
}
else {
NSLog(#"error: %#", error);
if (failureHandler)
failureHandler();
}
}];
}
- (void)requestMainPage {
//Now redirect to assignments page
NSURL *homeURL = [NSURL URLWithString:#"https://mistar.oakland.k12.mi.us/novi/StudentPortal/Home/PortalMainPage"];
NSMutableURLRequest *requestHome = [[NSMutableURLRequest alloc] initWithURL:homeURL];
[requestHome setHTTPMethod:#"GET"]; // this looks like GET request, not POST
[NSURLConnection sendAsynchronousRequest:requestHome queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *homeResponse, NSData *homeData, NSError *homeError)
{
// do whatever with the data...and errors
if ([homeData length] > 0 && homeError == nil) {
NSError *parseError;
NSDictionary *responseJSON = [NSJSONSerialization JSONObjectWithData:homeData options:0 error:&parseError];
if (responseJSON) {
// the response was JSON and we successfully decoded it
NSLog(#"Response was = %#", responseJSON);
} else {
// the response was not JSON, so let's see what it was so we can diagnose the issue
NSString *homePage = [[NSString alloc] initWithData:homeData encoding:NSUTF8StringEncoding];
NSLog(#"Response was not JSON (from home), it was = %#", homePage);
}
}
else {
NSLog(#"error: %#", homeError);
}
}];
}
Then, when you want to login, you can do something like:
[self loginToMistarWithPin:#"1234" password:#"pass" success:^{
[self requestMainPage];
} failure:^{
NSLog(#"login failed");
}];
Now, change those successHandler and failureHandler block parameters to include whatever data you need to pass back, but hopefully it illustrates the idea. Keep your methods short and tight, and use completion block parameters to specify what an asynchronous method should do when it's done.

Answer 2

Can you check the below link. It is about forcing one operation to wait for another.
NSOperation - Forcing an operation to wait others dynamically
Hope this helps.