RestKit RKObjectMapping to CLLocation

Question

我使用RestKit的对象映射将JSON数据映射到对象。是否可以将纬度和经度JSON属性映射到Objective-C类中的CLLocation变量？

JSON：

{ "items": [
    {
        "id": 1,
        "latitude": "48.197186",
        "longitude": "16.267452"
    },
    {
        "id": 2,
        "latitude": "48.199615",
        "longitude": "16.309645"
    }
]

}

它应该映射到的类：

@interface ItemClass : NSObject    
  @property (nonatomic, strong) CLLocation *location;
@end

最后，我想调用itemClassObj.location.longitude，从JSON响应中获取纬度值。

我以为像这样的东西会起作用，但它不是。

RKObjectMapping *mapping = [RKObjectMapping mappingForClass:[ItemClass class]];
[mapping mapKeyPath:@"latitude" toAttribute:@"location.latitude"];
[mapping mapKeyPath:@"longitude" toAttribute:@"location.longitude"];

非常感谢你的帮助。

Answer 1

要创建CLLocation，您需要同时提供纬度和经度。此外，CLLocation (像CLLocationCoordinate2D)的坐标不是NSNumbers，它们是双浮点数，所以它可以像这样提升映射中的键值遵从性，因为浮点数不是对象。

大多数情况下，人们会将纬度和经度作为NSNumbers存储在类中，然后在实例化/填充类对象后按需构建CLLocationCoordinate2D坐标。

如果您愿意的话，您可以利用willMapData: delegate方法来监听传入的数据，以便手动填充CLLocation ...但对我来说，这太夸张了，需要太多的开销。

EDIT:添加此代码，因为注释不会格式化代码属性...

或者，您可以在您的对象类实现和接口中放入类似这样的内容...

@property (nonatomic,readonly) CLLocationCoordinate2D coordinate;

- (CLLocationCoordinate2D)coordinate {
    CLLocationDegrees lat = [self.latitude doubleValue];
    CLLocationDegrees lon = [self.longitude doubleValue];
    CLLocationCoordinate2D coord = CLLocationCoordinate2DMake(lat, lon);
    if (NO == CLLocationCoordinate2DIsValid(coord))
        NSLog(@"Invalid Centroid: lat=%lf lon=%lf", lat, lon);
    return coord;
}

Answer 2

RestKit专门为CLLocation添加了一个ValueTransformer：

https://github.com/RestKit/RKCLLocationValueTransformer

给定示例JSON：

{
    "user": {
        "name": "Blake Watters",
        "location": {
            "latitude": "40.708",
            "longitude": "74.012"
        }
    }
}

要从给定的JSON映射到用户对象：

@interface User : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) CLLocation *location;
@end

使用RKCLLocationValueTransformer：

#import "RKCLLocationValueTransformer.h"

RKObjectMapping *userMapping = [RKObjectMapping mappingForClass:[User class]];
[userMapping addAttributeMappingsFromArray:@[ @"name" ]];
RKAttributeMapping *attributeMapping = [RKAttributeMapping attributeMappingFromKeyPath:@"location" toKeyPath:@"location"];
attributeMapping.valueTransformer = [RKCLLocationValueTransformer locationValueTransformerWithLatitudeKey:@"latitude" longitudeKey:@"longitude"];
[userMapping addPropertyMapping:attributeMapping];

RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:userMapping method:RKRequestMethodAny pathPattern:nil keyPath:@"user" statusCodes:[NSIndexSet indexSetWithIndex:200]];