Restkit 属性映射失败的转换错误

Question

这是我的示例代码的样子：

{
    "name": "Ahmad Mansour",
    "subjects": [
        {
            "parent_subject_name": "Arabic",
            "subject_name": "Shafahi",
            "exams": [
                {
                    "score": "30.00",
                    "exam_name": "Sa3i 1 "
                },
                {
                    "score": "50.00",
                    "exam_name": "sa3i 2"
                },
                {
                    "score": "100.00",
                    "exam_name": "First Semester Exam"
                }
            ]
        },
        {
            "parent_subject_name": "Arabic",
            "subject_name": "Khati",
            "exams": [
                {
                    "score": "50.00",
                    "exam_name": "Sa3i 1 "
                },
                {
                    "score": "60.00",
                    "exam_name": "sa3i 2"
                },
                {
                    "score": "95.00",
                    "exam_name": "First Semester Exam"
                }
            ]
        },

对于subject 实体.. 我的映射工作正常：

RKEntityMapping *subjectEntityMapping = [RKEntityMapping mappingForEntityForName:kSubjectIdentity inManagedObjectStore:model.managedObjectStore];
[subjectEntityMapping addAttributeMappingsFromDictionary:@{ @"subject_name": @"name",
                                                            @"parent_subject_name" :@"parent_name"
                                                          }];

subjectEntityMapping.identificationAttributes = @[ @"name" ];

RKResponseDescriptor *studentResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:subjectEntityMapping pathPattern:kGradesPath keyPath:@"subjects" statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

[model.objectManager addResponseDescriptor:studentResponseDescriptor];

但是当我做考试分数映射时..事情爆炸了：

RKEntityMapping *examEntityMapping = [RKEntityMapping mappingForEntityForName:kExamIdentity inManagedObjectStore:model.managedObjectStore];
[examEntityMapping addAttributeMappingsFromDictionary:@{ @"exams.exam_name": @"name" }];

examEntityMapping.identificationAttributes = @[ @"name" ];

RKResponseDescriptor *examResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:examEntityMapping pathPattern:kGradesPath keyPath:@"subjects" statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

[model.objectManager addResponseDescriptor:examResponseDescriptor];

我收到以下错误：

 E restkit.object_mapping:RKMappingOperation.m:431 Failed transformation of value at keyPath 'exams.exam_name' to representation of type 'NSString': Error Domain=org.restkit.RKValueTransformers.ErrorDomain Code=3002 "Failed transformation of value '(
    "Sa3i 1 ",
    "sa3i 2",
    "First Semester Exam"
)' to NSString: none of the 2 value transformers consulted were successful." UserInfo=0x9a508a0 {detailedErrors=(
    "Error Domain=org.restkit.RKValueTransformers.ErrorDomain Code=3002 \"The given value is not already an instance of 'NSString'\" UserInfo=0x9a50800 {NSLocalizedDescription=The given value is not already an instance of 'NSString'}",
    "Error Domain=org.restkit.RKValueTransformers.ErrorDomain Code=3000 \"Expected an `inputValue` of type `NSNull`, but got a `__NSArrayI`.\" UserInfo=0x9a50830 {NSLocalizedDescription=Expected an `inputValue` of type `NSNull`, but got a `__NSArrayI`.}"

我也试过这个映射，但我得到了完全相同的错误：

[examEntityMapping addAttributeMappingsFromDictionary:@{ @"exam_name": @"name" }];

examEntityMapping.identificationAttributes = @[ @"name" ];

RKResponseDescriptor *examResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:examEntityMapping pathPattern:kGradesPath keyPath:@"subjects.exams" statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

想法？

Answer 1

您不应该有考试的响应描述符。它是您的主题中的嵌套数据，因此应使用主题映射上的关系对其进行映射。

使用响应描述符不起作用，因为当映射只满足一个时，您试图映射到 2 个数组。因此，当 RestKit 尝试将数组转换为字符串时会出现错误。

此外，对于您的考试映射，您可能应该为唯一身份指定多个属性，因为考试名称会重复用于不同的实例...