iOS 中JSONModel的使用

Posted 2020-09-29 孙富有(iOS工程师)

涉想你的JSON数据像这样:

{ "id": "10", "country": "Germany", "dialCode": 49, "isInEurope": true }

• 为你的数据模型创建一个Objective-C的类，继承自JSONModel.
• 将JSON中的keys在.h文件中声明为属性:

#import "JSONModel.h"

@interface CountryModel : JSONModel

@property (assign, nonatomic) int id;
@property (strong, nonatomic) NSString* country;
@property (strong, nonatomic) NSString* dialCode;
@property (assign, nonatomic) BOOL isInEurope;

@end

在.m文件中不需要做任何事情.

• 用数据初始化你的model:

#import "CountryModel.h"
...

NSString* json = (fetch here JSON from Internet) ...
NSError* err = nil;
CountryModel* country = [[CountryModel alloc] initWithString:json error:&err];

举个例子

命名自动匹配

{
  "id": "123",
  "name": "Product name",
  "price": 12.95
}

@interface ProductModel : JSONModel
@property (assign, nonatomic) int id;
@property (strong, nonatomic) NSString* name;
@property (assign, nonatomic) float price;
@end

@implementation ProductModel
@end

模型嵌套 (模型包含其他模型)

{
  "order_id": 104,
  "total_price": 13.45,
  "product" : {
    "id": "123",
    "name": "Product name",
    "price": 12.95
  }
}

@interface OrderModel : JSONModel
@property (assign, nonatomic) int order_id;
@property (assign, nonatomic) float total_price;
@property (strong, nonatomic) ProductModel* product;
@end

@implementation OrderModel
@end

模型集合

{
  "order_id": 104,
  "total_price": 103.45,
  "products" : [
    {
      "id": "123",
      "name": "Product #1",
      "price": 12.95
    },
    {
      "id": "137",
      "name": "Product #2",
      "price": 82.95
    }
  ]
}

@protocol ProductModel
@end
@interface ProductModel : JSONModel
@property (assign, nonatomic) int id;
@property (strong, nonatomic) NSString* name;
@property (assign, nonatomic) float price;
@end

@implementation ProductModel
@end

@interface OrderModel : JSONModel
@property (assign, nonatomic) int order_id;
@property (assign, nonatomic) float total_price;
@property (strong, nonatomic) NSArray<ProductModel>* products;
@end

@implementation OrderModel
@end

注意: 尖括号后 NSArray 包含一个协议. 这跟Objective-C原生的泛型不是一个概念. 他们不会冲突, 但对于JSONModel来说,协议必须在一个地方声明.

key映射

{
  "order_id": 104,
  "order_details" : [
    {
      "name": "Product#1",
      "price": {
        "usd": 12.95
      }
    }
  ]
}

@interface OrderModel : JSONModel
@property (assign, nonatomic) int id;
@property (assign, nonatomic) float price;
@property (strong, nonatomic) NSString* productName;
@end

@implementation OrderModel

+(JSONKeyMapper*)keyMapper
{
  return [[JSONKeyMapper alloc] initWithDictionary:@{
    @"order_id": @"id",
    @"order_details.name": @"productName",
    @"order_details.price.usd": @"price"
  }];
}

@end

设置全局键映射(应用于所有model)

[JSONModel setGlobalKeyMapper:[
    [JSONKeyMapper alloc] initWithDictionary:@{
      @"item_id":@"ID",
      @"item.name": @"itemName"
   }]
];

设置下划线自动转驼峰

{
  "order_id": 104,
  "order_product" : @"Product#1",
  "order_price" : 12.95
}

@interface OrderModel : JSONModel

@property (assign, nonatomic) int orderId;
@property (assign, nonatomic) float orderPrice;
@property (strong, nonatomic) NSString* orderProduct;

@end

@implementation OrderModel

+(JSONKeyMapper*)keyMapper
{
  return [JSONKeyMapper mapperFromUnderscoreCaseToCamelCase];
}

@end

可选属性 (就是说这个属性可以为null或者为空)

{
  "id": "123",
  "name": null,
  "price": 12.95
}

@interface ProductModel : JSONModel
@property (assign, nonatomic) int id;
@property (strong, nonatomic) NSString<Optional>* name;
@property (assign, nonatomic) float price;
@property (strong, nonatomic) NSNumber<Optional>* uuid;
@end

@implementation ProductModel
@end

忽略属性 (就是完全忽略这个属性)

{
  "id": "123",
  "name": null
}


@interface ProductModel : JSONModel
@property (assign, nonatomic) int id;
@property (strong, nonatomic) NSString<Ignore>* customProperty;
@end

@implementation ProductModel
@end

设置所有的属性为可选(所有属性值可以为空)

@implementation ProductModel
+(BOOL)propertyIsOptional:(NSString*)propertyName
{
  return YES;
}
@end

使用JSONModel自带的 HTTP 请求

//add extra headers
[[JSONHTTPClient requestHeaders] setValue:@"MySecret" forKey:@"AuthorizationToken"];

//make post, get requests
[JSONHTTPClient postJSONFromURLWithString:@"http://mydomain.com/api"
                                   params:@{@"postParam1":@"value1"}
                               completion:^(id json, JSONModelError *err) {

                                   //check err, process json ...

                               }];

将model转化为字典或者json格式的字符串

ProductModel* pm = [[ProductModel alloc] initWithString:jsonString error:nil];
pm.name = @"Changed Name";

//convert to dictionary
NSDictionary* dict = [pm toDictionary];

//convert to text
NSString* string = [pm toJSONString];

自定义数据的转换

@implementation JSONValueTransformer (CustomTransformer)

- (NSDate *)NSDateFromNSString:(NSString*)string {
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:APIDateFormat];
    return [formatter dateFromString:string];
}

- (NSString *)JSONObjectFromNSDate:(NSDate *)date {
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:APIDateFormat];
    return [formatter stringFromDate:date];
}

@end

自定义处理指定的属性

@interface ProductModel : JSONModel
@property (assign, nonatomic) int id;
@property (strong, nonatomic) NSString* name;
@property (assign, nonatomic) float price;
@property (strong, nonatomic) NSLocale *locale;
@end

@implementation ProductModel

// Convert and assign the locale property
- (void)setLocaleWithNSString:(NSString*)string {
    self.locale = [NSLocale localeWithLocaleIdentifier:string];
}

- (NSString *)JSONObjectForLocale {
    return self.locale.localeIdentifier;
}

@end

自定义JSON校验

@interface ProductModel : JSONModel
@property (assign, nonatomic) int id;
@property (strong, nonatomic) NSString* name;
@property (assign, nonatomic) float price;
@property (strong, nonatomic) NSLocale *locale;
@property (strong, nonatomic) NSNumber <Ignore> *minNameLength;
@end

@implementation ProductModel

- (BOOL)validate:(NSError *__autoreleasing *)error {
    BOOL valid = [super validate:error];

    if (self.name.length < self.minNameLength.integerValue) {
        *error = [NSError errorWithDomain:@"me.mycompany.com" code:1 userInfo:nil];
        valid = NO;
    }

    return valid;
}

@end