iOS / Objective-C - 如何在不丢失初始会话的情况下发送多个NSURLSessionDataTask请求？

Question

I am currently working on a project in an iOS programming course. As part of a class project I am working to make a particular portion work successfully.

I am using an NSAlert dialog to supply my login and password to fetch my enrolled classes in an HTML string.

My college maintains students' enrolled class schedule on the college information system from which I can log in and see my classes.

I want to log in to the college webpage that has a page called submit.asp to process POST requests sent from a login form. On an actual browser, when I submit my credentials, and after some the server processes and redirects to another page I am able to navigate to my class schedule page with no problem.

- (BOOL) loginToStudentPortal: (NSString *) ID : (NSString *) pin
{
    NSString *submitUrl = @"https://eweb4.laccd.edu/Common/submit.asp";
    NSString *scheduleUrl = @"https://eweb4.laccd.edu/WebStudent/validate.asp";

    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];
    manager.responseSerializer = [AFHTTPResponseSerializer serializer];
    NSURL *URL = [NSURL URLWithString:submitUrl];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL];

    NSString * submitParams = [NSString stringWithFormat:@"ssn1=%@&ssn2=&pin=%@REDIRECT/WebStudent/validate.asp", ID, pin];
    NSString * submitParams2 = [NSString stringWithFormat:@"HOLDER=Y"];
    [request setHTTPMethod:@"POST"];
    [request setHTTPBody:[submitParams dataUsingEncoding:NSUTF8StringEncoding]];

    NSURLSessionDataTask *dataTask = [manager dataTaskWithRequest:request completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) {
        if (error) {
           NSLog(@"%@", error);
        } else {
           //Here I Try to initiate a second dataTaskWithRequest to the next URL
           //But there is no way to jump to the destination page without losing the session

           //NSString *receivedData = [[NSString alloc] initWithData:responseObject encoding:NSASCIIStringEncoding];
           //NSLog(@"%@ %@", response, receivedData);

    }];
    [dataTask resume];
    return YES;
}

However, when I run the initial request from the iPhone simulator in XCode 5, I can not get the session preserved after the first request.

Is it correct to attempt to initiate a follow on dataTask request in the else block of the main completionHandler?

Secondly, do I need to do make sure manually that I follow any redirects from the server?

Answer 1

I was able to resolve the issue and finally get to the destination page.

My initial attempt was a start, but I continued to investigate the behavior further and it seems that one reason I was not able to proceed was that I was debugging and I think the timeout was occurring.

When I ran the program and removed all breakpoints the program would output the correct HTML.

More importantly, I made sure that the exact chain of events was reproduced in my function. I added all the dataTasks required within the completion handlers.

I was eventually able to retrieve the HTML string containing the desired information.

It turns out the session is managed by the method I was using. Probably I had a session timeout which is why I posed the initial question.