如何在Restkit中映射自定義錯誤鍵？

Question

當用戶在我們的服務器上籤約成功，它以200狀態碼和JSON有效載荷這樣的迴應：

{ 
    "error": null, 
    "result": { 
     "auth": { 
      "created_utc": 1420740197, 
      "device_token": "rQZJddrbD5tyEpznb8bVKeGlHqRNGyvOgDR;tQJBkpkfAXO6DQ4lNiG17lzu6IDc0hVBfR3RrN9o0txRQIYAa6fnf5d9LNaSRDMk9LrplgkITuMC37v;;;rvG35CJvV7dWZ5TQVYUWeHwAABvKvzTRpSDw5Qg9jQrmiUHLZptegFY=76421420740197" 
     }, 
     "display_name": "a", 
     "email": "a@a.com", 
     "user_id": 7642, 
     "username": "a" 
    } 
} 

但如果a@a.com嘗試重新註冊時，其與響應400狀態碼和有效載荷JSON這樣的：

{ 
    "error": { 
     "code": 805, 
     "message": "there is another user with that username" 
    }, 
    "result": null 
} 

我試圖映射誤差，這樣，當Restkit返回一個錯誤，我得到的消息，以及該代碼。這些都是我想做到這一點的方法：

RKObjectMapping *errorMapping = [RKObjectMapping mappingForClass:[RKErrorMessage class]]; 
[errorMapping addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:@"error.message" toKeyPath:@"errorMessage"]]; 

RKResponseDescriptor *errorDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:errorMapping method:RKRequestMethodAny pathPattern:nil keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassClientError)]; 

[self.objectManager addResponseDescriptor:errorDescriptor]; 

這其中顯然只得到了錯誤的消息部分與該輸出返回：

Error Domain=org.restkit.RestKit.ErrorDomain Code=1004 "there is another user with that username" UserInfo=0x7feefcf8a730 {RKObjectMapperErrorObjectsKey=(
"there is another user with that username" 
), NSLocalizedDescription=there is another user with that username} 

於是我試圖使RKErrorMessage的子類：

#import "RKErrorMessage.h" 

@interface TAG_RKErrorMessage : RKErrorMessage 

@property (strong, nonatomic) NSNumber *errorCode; 

@end 

，改變了映射到這一點：

RKObjectMapping *errorMapping = [RKObjectMapping mappingForClass:[TAG_RKErrorMessage class]]; 
[errorMapping addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:@"error.message" toKeyPath:@"errorMessage"]]; 
[errorMapping addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:@"error.code" toKeyPath:@"errorCode"]]; 

並導致完全相同的輸出：

Error Domain=org.restkit.RestKit.ErrorDomain Code=1004 "there is another user with that username" UserInfo=0x7fa16c627ce0 {RKObjectMapperErrorObjectsKey=(
"there is another user with that username" 
), NSLocalizedDescription=there is another user with that username} 

所以最後我想這映射到至少嘗試獲得字典顯示爲的RKObjectMapperErrorObjectsKey的NSError的userInfo：

RKObjectMapping *errorMapping = [RKObjectMapping mappingForClass:[RKErrorMessage class]]; 
[errorMapping addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:@"error" toKeyPath:@"errorMessage"]]; 

而導致這種輸出：

Error Domain=org.restkit.RestKit.ErrorDomain Code=1004 "<null>" UserInfo=0x7ff8abe678e0 {RKObjectMapperErrorObjectsKey=(
(null) 
), NSLocalizedDescription=<null>} 

現在我被困在這一點上。如何映射服務器錯誤響應的密鑰，以便我可以訪問返回的code以及message作爲兩個單獨的值？

Answer 1

您可能已正確映射了您的TAG_RKErrorMessage實例。你有沒有試圖從你得到的NSError中提取它？您可以使用RKObjectMapperErrorObjectsKey作爲對NSError的用戶信息詞典一鍵搞定所有映射的錯誤消息的數組：

NSArray* objectMapperErrorObjectsArray = [error.userInfo objectForKey:RKObjectMapperErrorObjectsKey]; 

然後，您可以遍歷數組檢查每個錯誤要回應的條件，例如，如果你想與錯誤信息「無效令牌」 403響應代碼作出反應，你可以這樣做：

NSArray* objectMapperErrorObjectsArray = [error.userInfo objectForKey:RKObjectMapperErrorObjectsKey]; 
for (RKErrorMessage* objectMapperErrorObject in objectMapperErrorObjectsArray) 
{ 
    if ([objectMapperErrorObject.errorMessage isEqual:@"Invalid token"]) 
    { 
     if (operation.HTTPRequestOperation.response.statusCode == 403) 
     { 
      //Code to handle a 403 response status code when error message is "Invalid token". 
     } 
    } 
} 

Answer 2

只是一個提示：如果你想使用內置的RKErrorMessage而無需創建任何子類，都可以將所有錯誤的JSON屬性映射到RKErrorMessage.userInfo這樣：

Objective-C的：

RKObjectMapping *errorMapping = [RKObjectMapping mappingForClass:[RKErrorMessage class]]; 
[errorMapping addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:nil toKeyPath:@"userInfo"]]; 

RKResponseDescriptor *errorDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:errorMapping method:RKRequestMethodAny pathPattern:nil keyPath:"error" statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassClientError)]; 

斯威夫特：

let errorMapping = RKObjectMapping(forClass: RKErrorMessage.self); 
errorMapping.addPropertyMapping(RKAttributeMapping(fromKeyPath: nil, toKeyPath: "userInfo")); 

let errorResponseDescriptor = RKResponseDescriptor(
    mapping: errorMapping, 
    method: RKRequestMethod.Any, 
    pathPattern: nil, 
    keyPath: "error", 
    statusCodes: RKStatusCodeIndexSetForClass(UInt(RKStatusCodeClassClientError))) 
);