Obj-C: Pass method arguments to nested block - ios

Question

I am using AFNetworking to consume some JSON data. I have to do this in a number of my view controllers. I'm trying to refactor my code and remove some duplication. I would like to know how I could pass, for instance, a NSArray object to the completion block of AFHTTPRequestOperation?
I have attempted the following to no avail.
-(void)request:(NSArray *)jsonArray
{
// ...
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
[operation setCompletionBlockWithSuccess:
^(AFHTTPRequestOperation *operation, id responseObject) {
jsonArray = responseObject;
dispatch_async(dispatch_get_main_queue(),
^{
[self.tableView reloadData];
}
);
}
failure:
^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Request Failed: %#, %#", error, error.userInfo);
}
];
[operation start];
}

Answer 1

It sounds like you want jsonArray to be an out method parameter so you can set its value within your method. With an asynchronous request like you have here this is heavily discouraged, but nonetheless.
Your method definition would change to:
-(void)request:(out NSArray **)jsonArray;
Calls to this method would change to:
[object request:&anArray];
And your completion handler would set the array with:
*jsonArray = responseObject;
For what it's worth, I agree with CrimsonChris who suggested using a callback block to handle this properly.

Answer 2

In case I understand you, I can advice you to do like this:
-(void)request:(NSArray *)jsonArray
compltition:(void(^)(NSDIctionary *response))complition {
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
[operation setCompletionBlockWithSuccess:
^(AFHTTPRequestOperation *operation, id responseObject) {
jsonArray = responseObject;
dispatch_async(dispatch_get_main_queue(),
^{
//returning response
complition(response);
[self.tableView reloadData];
}
);
}
failure:
^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Request Failed: %#, %#", error, error.userInfo);
}
];
[operation start];
}
and where you are calling this function:
[self request:jsonArray complition:^(NSDictionary *response) {
NSLog(#"Response = %#, response")
//and you can parse and reload your table
}];

Answer 3

I solved this by defining the function in a helper class, making jsonArray an instance variable of that class, instead of a function argument.