Incompatible block pointer types - iOS - ios

Question

I have an iOS app with a function which is in charge of making an asynchronous network request. The request itself works just fine, but the problem I am having is with the function return statement which is causing errors.
Here is my function:
-(NSArray *)get_data:(NSString *)size {
// Set up the data request.
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:#"http://mywebsite.com/info.json"]];
NSURLRequest *url_request = [NSURLRequest requestWithURL:url];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
// Begin the asynchronous data loading.
[NSURLConnection sendAsynchronousRequest:url_request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
if (error == nil) {
// Convert the response JSON data to a dictionary object.
NSError *my_error = nil;
NSDictionary *feed = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:&my_error];
if (feed != nil) {
// Store the returned data in the data array.
NSArray *topping_data;
for (int loop = 0; loop < [[feed objectForKey:#"toppings_data"] count]; loop++) {
NSString *size_name = [NSString stringWithFormat:#"%#", [[[feed objectForKey:#"toppings_data"] objectAtIndex:loop] valueForKey:#"Size"]];
if ([size_name isEqualToString:size]) {
topping_data = [[feed objectForKey:#"toppings_data"] objectAtIndex:loop];
}
}
return topping_data;
}
else {
return #[#"no data"];
}
}
else {
return #[#"no data"];
}
}];
}
I am getting the following error message on the line of code [NSURLConnection sendAsync....:
Incompatible block pointer types sending 'NSArray *(^)(NSURLResponse
*__strong, NSData *__strong, NSError *__strong)' to parameter of type 'void (^ _Nonnull)(NSURLResponse * _Nullable __strong, NSData *
_Nullable __strong, NSError * _Nullable __strong)'
What am I doing wrong here?
All I am trying to avoid, is the function returning BEFORE the asynchronous request has completed. Otherwise the function will not return any data, which is not what I want.
Thanks for your time, Dan.

Answer 1

best way to return data in async block is make a block callback as argument of function and callback return value here:
- (void)get_data:(NSString *)size completionHandler:(void (^)(NSArray *array))completionHandler {
// ...
[NSURLConnection sendAsynchronousRequest:url_request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
// ...
completionHandler(array);
// ...
}];
}
use :
[self get_data:someString completionHandler:^(NSArray *array) {
// process array here
}];

Answer 2

The block returns nothing:
void ^(NSURLResponse *, NSData *, NSError *)
So you cannot return things:
return #[#"no data"];
The code that calls the block is not interested in what it returns; if you want to store state then add an instance variable or call a method.

Answer 3

Change
[NSURLConnection sendAsynchronousRequest:url_request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
to
[NSURLConnection sendAsynchronousRequest:url_request queue:queue completionHandler:^(NSURLResponse *_Nullable response, NSData *_Nullable data, NSError *_Nullable error)