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