Question

I have an app that uses a segmentedControl. First item is an “All” item, where the rest is created from an array based on result from webservice. When “All” is selected I want to request all the request.

How can I go about this,

NSArray *urls = [NSArray arrayWithObjects:@"http://service/group/1/", 
                                          @"http://service/group/2/", nil];

I want to collect all result from the calls into a collection and display it in a UITableView when the “All” item is selected and probably in viewDidLoad.
For the other segments only one of the request is issued and callback with an array that then is used in:

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

I have tried to look at this example for making the request from the array MultipleDownloads

Thanks,

The method in my viewController to initiate the multiple download:

- (void)requestChildrenInBackground {

queue = [[NSOperationQueue alloc] init];

//Todo remove hard coded and get from previous request respons
NSArray *urls = [NSArray arrayWithObjects: @"http://service/1/children", 
                @"http://service/2/children",
                @"http://service/3/children", nil];

NSLog(@"%@", urls);    
for (NSString * url in urls)
{
    GetSchedule *operation =
    [GetSchedule urlDownloaderWithUrlString:url];
    [queue addOperation:operation];
}
}

This is how the multiple request gets handled:

#import "GetSchedule.h"

#import "JSON.h"
#import "Authentication.h"
#import "AttendanceReportViewController.h"

@interface GetSchedule ()

- (void)finish;

@end

@implementation GetSchedule

@synthesize appDelegate;

@synthesize username;
@synthesize password;
@synthesize authenticationString;
@synthesize encodedLoginData;
@synthesize schedulesArray;

@synthesize url = _url;
@synthesize statusCode = _statusCode;
@synthesize data = _data;
@synthesize error = _error;
@synthesize isExecuting = _isExecuting;
@synthesize isFinished = _isFinished;

+ (id)urlDownloaderWithUrlString:(NSString *)urlString {

NSURL * url = [NSURL URLWithString:urlString];
GetSchedule *operation = [[self alloc] initWithUrl:url];
return [operation autorelease];
}

- (id)initWithUrl:(NSURL *)url {

self = [super init];
if (self == nil)
    return nil;

_url = [url copy];
_isExecuting = NO;
_isFinished = NO;

return self;
}

- (void)dealloc
{
[username release];
[password release];
[encodedLoginData release];

[_url release];
[_connection release];
[_data release];
[_error release];
[super dealloc];
}

 - (BOOL)isConcurrent
{
return YES;
}

- (void)start
{
if (![NSThread isMainThread])
{
    [self performSelectorOnMainThread:@selector(start) withObject:nil waitUntilDone:NO];
    return;
}
self.username = appDelegate.username;
self.password = appDelegate.password;

Authentication *auth = [[Authentication alloc] init];
authenticationString = (NSMutableString*)[@"" stringByAppendingFormat:@"%@:%@", username, password];    
self.encodedLoginData = [auth encodedAuthentication:authenticationString];
[auth release];

NSLog(@"operation for <%@> started.", _url);

[self willChangeValueForKey:@"isExecuting"];
_isExecuting = YES;
[self didChangeValueForKey:@"isExecuting"];

// Setup up the request with the url
NSMutableURLRequest *request = [[NSMutableURLRequest alloc]
                                initWithURL:_url];

[request setHTTPMethod:@"GET"];
[request setValue:[NSString stringWithFormat:@"Basic %@", encodedLoginData] forHTTPHeaderField:@"Authorization"];

_connection = [[NSURLConnection alloc] initWithRequest:request
                                              delegate:self];
if (_connection == nil)
    [self finish];
else {
    _data = [[NSMutableData alloc] init];
}

 }

  - (void)finish
{
NSLog(@"operation for <%@> finished. "
      @"status code: %d, error: %@, data size: %u",
      _url, _statusCode, _error, [_data length]);

[_connection release];
_connection = nil;

[self willChangeValueForKey:@"isExecuting"];
[self willChangeValueForKey:@"isFinished"];

_isExecuting = NO;
_isFinished = YES;

[self didChangeValueForKey:@"isExecuting"];
[self didChangeValueForKey:@"isFinished"];
 }

#pragma mark -
#pragma mark NSURLConnection delegate

 - (void)connection:(NSURLConnection *)connection
didReceiveResponse:(NSURLResponse *)response
 {
//[_data release];
//_data = [[NSMutableData alloc] init];

[_data setLength:0];

NSHTTPURLResponse * httpResponse = (NSHTTPURLResponse *)response;
_statusCode = [httpResponse statusCode];
}

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

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
// Parse the responseData of json objects retrieved from the service
SBJSON *parser = [[SBJSON alloc] init];

NSString *jsonString = [[NSString alloc] initWithData:_data encoding:NSUTF8StringEncoding];
NSDictionary *jsonData = [parser objectWithString:jsonString error:nil];
NSMutableArray *array = [jsonData objectForKey:@"Children"];

schedulesArray = [NSMutableArray array];
[schedulesArray addObject:array];

// Callback to AttendanceReportViewController that the responseData finished loading
[attendanceReportViewController loadSchedule];  

[self finish];

}

 - (void)connection:(NSURLConnection *)connection
 didFailWithError:(NSError *)error
 {
 _error = [error copy];
 [self finish];
 }

@end

When all data is received I want to call back to my ViewController and get an array with all data from all request made.

Answer 1

Create a downloader

1. Create a downloader class using NSURLConnection.
2. Keep a member variable called downloaderObjectId.
3. Write a delegate method for this object. This method will pass the downloaded data and downloaderObjectId back to the delegate.

In the delegate.

1. Create multiple downloader objects(As per your ncessity) with unique value for the downloaderObjectId.

2. Store these objects in a NSMutableDictionary

3. Key for each object will be downloaderObjectId. so that when the delegate method is called after download you take the exact object back from the NSMutableDictionary using this key.

Main point.

1. Each time delegate is called. You should remove the object from dictionary(The object who is done with the download and called his delgate. You can identify this object by the key downloaderObjectId he holds. )

2. Then check the count of dictionary. If it is zero you can make sure that your downloads are completed. So you can call your viewcontroller.