我希望使用RestKit开发一款能够在线下和离线状态下运行的应用程序。
我可能对RestKit的工作方式有所误解,但我认为这个实现起来相对容易。
在一个简单的iOS测试应用程序中,我按照以下步骤设置了环境:
// setup the client
NSString* URL = @"http://10.211.55.5:3000/api";
RKClient* client = [RKClient clientWithBaseURL:URL];
client.username = @"me@email.com";
client.password = @"password";
// setup caching
client.cachePolicy = RKRequestCachePolicyLoadIfOffline | RKRequestCachePolicyLoadOnError | RKRequestCachePolicyTimeout;
client.requestCache.storagePolicy = RKRequestCacheStoragePolicyPermanently;
// setup managed object store
RKObjectManager* objectManager = [RKObjectManager objectManagerWithBaseURL:URL];
RKManagedObjectStore* objectStore = [RKManagedObjectStore objectStoreWithStoreFilename:@"RestKitCoreDataTest.sqlite"];
// connect my cache implementation
MyCache* cache = [[MyCache alloc] init];
objectStore.managedObjectCache = cache;
objectManager.objectStore = objectStore;
// setup mapping
RKManagedObjectMapping* userMapping = [RKManagedObjectMapping mappingForClass:[User class]];
[userMapping mapKeyPath:@"id" toAttribute:@"identifier"];
[userMapping mapKeyPath:@"email" toAttribute:@"email"];
[userMapping mapKeyPath:@"firstname" toAttribute:@"firstname"];
[userMapping mapKeyPath:@"surname" toAttribute:@"surname"];
userMapping.primaryKeyAttribute = @"identifier";
[objectManager.mappingProvider setMapping:userMapping forKeyPath:@""];
// setup routes
RKObjectRouter* router = [objectManager router];
[router routeClass:[User class] toResourcePath:@"/users/:identifier"];
用户对象是为了支持CoreData而实现的必需对象:
@interface User : NSManagedObject
@property (nonatomic, retain) NSNumber * identifier;
@property (nonatomic, retain) NSString * email;
@property (nonatomic, retain) NSString * firstname;
@property (nonatomic, retain) NSString * surname;
@end
@implementation User
@dynamic identifier;
@dynamic email;
@dynamic firstname;
@dynamic surname;
@end
这是我的缓存(MyCache)。请注意,我没有费心去检查resourcePath
,因为这只是为了尝试一些东西,而且我已经有一个路径了。
@implementation MyCache
- (NSArray*)fetchRequestsForResourcePath:(NSString*)resourcePath
{
NSFetchRequest* fetchRequest = [User fetchRequest];
return [NSArray arrayWithObject:fetchRequest];
}
-(BOOL)shouldDeleteOrphanedObject:(NSManagedObject *)managedObject
{
return true;
}
@end
然后我通过路径"/api/users/123"向服务器发出请求,以获取ID为123的用户:
User* user = [User object];
user.identifier = [NSNumber numberWithInt:123];
RKObjectManager* manager = [RKObjectManager sharedManager];
[manager getObject:user delegate:self];
这个工作正常。但是,当我断开我的Mac上的WiFi时,上面的代码无法从sqlite数据库中检索用户。
相反,在代理的objectLoader:didFailWithError
中我会得到以下错误:
2012-03-01 11:44:09.402 RestKitCoreDataTest[1989:fb03] error: Error Domain=NSURLErrorDomain Code=-1001 "The request timed out." UserInfo=0x6b89aa0 {NSErrorFailingURLStringKey=http://10.211.55.5:3000/api/users/123, NSErrorFailingURLKey=http://10.211.55.5:3000/api/users/123, NSLocalizedDescription=The request timed out., NSUnderlyingError=0x6b81ac0 "The request timed out."}
我认为通过指定缓存应在超时时使用:"RKRequestCachePolicyTimeout",我期望能从本地缓存中检索到用户。
缓存确实包含带有ID 123的用户记录 - 在ZUSER表中,其中123在ZIDENTIFIER列中。
我是否漏掉了某个步骤才能让它起作用?也许还需要处理另一个委托方法,或者在超时后命中缓存时调用该方法?或者我试图做一些RestKit默认情况下不支持的事情?
干杯。