new blog post, albert rest kit

source/_posts/2013-09-03-global-request-management-with-restkit.markdown

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+---
+layout: post
+title: "Global response management with RestKit"
+date: 2013-09-03 13:15
+comments: true
+categories: ios restkit
+description: "RESTKIT how to handle request failures global"
+---
+
+For our latest iOS app we are using [RestKit Framework](http://restkit.org), which is a really great and advanced library to communicate to your REST API.
+
+When you have lots of requests in different areas of your project, you may want to have a global handling for failure events.
+For example how an Login View, if any of the requests gives you an 401 (Unauthorized) status code.
+
+In RestKit 0.20 they introduced the oppertunity to register your own `RKObjectRequestOperation`, which is the common way to do this.
+
+So at first you create a subclass of `RKObjectRequestOperation`, let's call it `CustomRKObjectRequestOperation`
+
+```objective-c
+
+#import "RKObjectRequestOperation.h"
+
+@interface CustomRKObjectRequestOperation : RKObjectRequestOperation
+
+@end
+
+@implementation CustomRKObjectRequestOperation
+
+- (void)setCompletionBlockWithSuccess:(void ( ^ ) ( RKObjectRequestOperation *operation , RKMappingResult *mappingResult ))success failure:(void ( ^ ) ( RKObjectRequestOperation *operation , NSError *error ))failure
+{
+    [super setCompletionBlockWithSuccess:^void(RKObjectRequestOperation *operation , RKMappingResult *mappingResult) {
+        if (success) {
+            success(operation, mappingResult);
+        }
+        
+    }failure:^void(RKObjectRequestOperation *operation , NSError *error) {
+        
+        [[NSNotificationCenter defaultCenter] postNotificationName:@"connectionFailure" object:operation];
+        
+        if (failure) {
+            failure(operation, error);
+        }
+        
+    }];
+}
+
+@end
+
+```
+This is the point where we overwrite the method which sets the completion and failure block.
+I use the Observer Pattern (`NSNotificationCenter`) to notify about connectionFailures. ([Learn more about NSNotificationCenter](http://mobile.tutsplus.com/tutorials/iphone/ios-sdk_nsnotificationcenter/))  
+
+Of course we need to tell RestKit to use our custom `RKObjectRequestOperation` class. You can do this by adding this line to you RestKit configuration:
+```objective-c
+[[RKObjectManager sharedManager] registerRequestOperationClass:[CustomRKObjectRequestOperation class]];
+```
+
+
+Now we need a class where we listen to the failure notifications. You can choose any of your class, I use the AppDelegate for this.
+```objective-c
+[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(connectionFailedWithOperation:) name:@"connectionFailure" object:nil];
+```
+
+As you should know, the `connectionFailedWithOperation:` is called when a connection failure occures.
+```objective-c
+- (void)connectionFailedWithOperation:(NSNotification *)notification
+{
+    RKObjectRequestOperation *operation = (RKObjectRequestOperation *)notification.object;
+    if (operation) {
+        
+        NSInteger statusCode = operation.HTTPRequestOperation.response.statusCode;
+
+        switch (statusCode) {
+            case 0: // No internet connection
+            {
+            }
+                break;
+            case  401: // not authenticated
+            {
+            }
+                break;
+                
+            default:
+            {
+            }
+                break;
+        }
+    }
+}
+```
+
+Links:  
+[RestKit Framework](http://restkit.org)  
+[Class Documentation for RKObjectRequestOperation](http://restkit.org/api/latest/Classes/RKObjectRequestOperation.html)
+
+_by Albert Schulz_  
+If you have any questions feel free to contact me:  
+eMail: mail@halfco.de  
+Twitter: [@albert_sn](https://twitter.com/albert_sn)  
+Web: [halfco.de](http://halfco.de)  
+