How can I refactor duplicated codes for error? - objective-c

Question

I'm using block for my APIs and the API class throws error via block like below code.
[HJHLifeAPI deletePlantWithIdentifier:identifier completionHandler:^(NSError *error) {
if (error) {
[[error alertView] show];
return ;
}
[self refresh:self.refreshControl];
}];
But the problem is that I use this pattern of codes in several places. As a result, I should write several duplicated codes for error handling. Is there any way to refactor this code? I think exception can be one solution, but I think Apple don't encourage developers to use it.

Answer 1

It's up to How your HJHLifeAPI is designed.
I usually use AFNetworking for API things and here's an example.
// This is the method like deletePlantWithIdentifier:
// It actually invoke __requestWitPath:
- (void)requestSomethingWithId:(NSString *)memId done:(NetDoneBlock)done
{
NSMutableDictionary *param_ = #{#"key":#"id"};
[self __requestWithPath:#"/apiPath.jsp" parameter:param_ done:done];
}
#pragma PRIVATE
- (void)__requestWithPath:(NSString *)apiPath parameter:(NSDictionary *)parameter done:(NetDoneBlock)done
{
AFHTTPRequestOperationManager *manager = [[AFHTTPRequestOperationManager alloc] initWithBaseURL:[NSURL URLWithString:SERVER_URL]];
AFHTTPRequestOperation *operation = [manager POST:apiPath parameters:parameter constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
} success:^(AFHTTPRequestOperation *operation, id responseObject) {
done();
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
// Error Handle Here
}];
[operation start];
}
You can handle all errors in one __request....

Answer 2

Create the block
void(^errorHandler)(NSError *error) = ^(NSError *error) {
if (error) {
[[error alertView] show];
return ;
}
[self refresh:self.refreshControl];
}
Save it somewhere (don't forget to copy it)
self.errorHandler = errorHandler;
Reuse it everywhere:
[HJHLifeAPI deletePlantWithIdentifier:identifier completionHandler:self.errorHandler];