How to make one function that organizes multiple NSURLSessionDataTask (s)? [closed] - ios

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After creating an NSURLSession, it appears that making multiple web queries with NSURLSessionDataTask can lead to some code writing redundancy, which I'd like to clean up. The following code is repeated multiple times:
NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
}];
[task resume];
Could the task be initiated from inside a dedicated function? It would be easy to pass in the NSMutableURLRequest as a variable but what about the completion handler?
Theoretically you could pass in the completion handler as a block, right? The problem I ran into is that the callback variables (data & response) can't be referred to from outside the provided completion handler, so how can you write a block that refers to them?
Right now I have 3 or 4 separately written tasks going, and it looks like it may stay that way unless someone has an idea!
EDIT, SOLUTION:
The method definition is:
- (void) engage:(NSMutableURLRequest *)request with:(void (^)(NSData *, NSURLResponse *, NSError *))yourmom;
& The block literal that it takes looks like:
void (^yourmom)(NSData *, NSURLResponse *, NSError *) = ^(NSData *data, NSURLResponse *response, NSError *error) {
// stuff
};
Basically, the key thing I was missing was that I needed my block to accept variables so that I could refer to them by name without compiler errors. The above code creates a variable-accepting block which lets me get around the compiler warnings about out of scope variables. Also if the code
[self engage:request with:yourmom];
shows up somewhere we'll know where it came from.

Answer 1

If you're asking how can you pass the completion block to the utility method, you should just supply a block parameter to your method:
- (NSURLSessionDataTask *)startDataTaskWithRequest:(NSURLRequest *)request completionHandler:(void (^)(NSData *data, NSURLResponse *response, NSError *error))block
{
NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:block];
[task resume];
return task;
}
Or, if there are portions of the completion block which you're repeating all the time, then go ahead and put that in your utility method, but then invoke the caller's block:
- (NSURLSessionDataTask *)startDataTaskWithRequest:(NSURLRequest *)request completionHandler:(void (^)(NSData *data, NSURLResponse *response, NSError *error))block
{
NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error){
// do here stuff that I'll always do, such as logging errors, checking response codes, etc.
// when that's done, I can now invoke the caller's block
if (block) {
block(data, response, error);
}
}];
[task resume];
return task;
}

Answer 2

I'd say make a category on NSURLSession and do the following:
First typedef a completion block in the header file:
typedef void (^NSURLSessionDataTaskCompletionHandler) (NSData *data, NSURLResponse *response, NSError *error);
Then add a method to the header file:
- (NSURLSessionDataTask *)startTaskWithRequest:(NSURLRequest *)request completionHandler:(NSURLSessionDataTaskCompletionHandler)completionHandler;
Finally the body of the function in the implementation file:
- (NSURLSessionDataTask *)startTaskWithRequest:(NSURLRequest *)request completionHandler:(NSURLsessionDataTaskCompletionHandler)completionHandler
{
NSURLSessionDataTask *task = [self dataTaskWithRequest:request completionHandler:completionHandler];
[task resume];
return task;
}
Now you get to very easily do something like:
[session startTaskWithRequest:request completionHandler:(NSData *data, NSURLResponse *response, NSError *error){
// do stuff
}];