iOS中JSON与NSObject互转有两种方式：1、iOS自带类NSJSONSerialization 2、第三方开源库SBJSON、JSONKit、MJExtension。项目中一直用MJExtension来进行JSON与Model的互转，非常方便、强大，接下来介绍一下这个轻量、强大的开源库。

1、什么是MJExtension？

MJExtension是一套字典和模型之间互相转换的轻量级开源框架，github地址为：GitHub - CoderMJLee/MJExtension: A fast。功能如下：

JSON --> Model、Core Data Model

JSONString --> Model、Core Data Model

Model、Core Data Model --> JSON

JSON Array --> Model Array、Core Data Model Array

JSONString --> Model Array、Core Data Model Array

Model Array、Core Data Model Array --> JSON Array

Model Coding（归档和接档）

MJExtension特性在于JSON与Model的互转，避免了用NSJSONSerialization或者SBJSON、JSONKit等非Model解析库把JSON解析出成NSDictionary后到处用valueForKey或者objectForKey方法获取字段相应值所带来的麻烦，尤其是要在不同类之间传输数据的时候，传Model比传NSDictionary这种方式实在是方便、优雅太多了

2、MJExtension架构

1）UML类图

2）类介绍

NSObject+MJKeyValue(Model辅助类,提供字典字段到Model相应的属性转换)

NSObject+MJProperty(Model辅助类，封装Model属性操作)

MJProperty(Model属性封装类)

MJType(Model属性类型封装类)

NSObject(MJCoding)(Model归档和解档封装类)

3、MJExtension JSON转Model流程图

4、MJExtension用法举例

关于用法详情请见：GitHub - CoderMJLee/MJExtension: A fast。我这里只介绍两种常用的用法，JSON转Model，JSON转Model数组

@interface PersonModel : NSObject

@property (nonatomic, copy) NSString* name;

@property (nonatomic, copy) NSString* sex;

@property (nonatomic, copy) NSString* age;

- (void)fetchPerson

{

__weak typeof(self)weakSelf = self;

fetchPersonRequest* request = [[fetchPersonRequest alloc] init];

[request startWithCompletionBlockWithSuccess:^(YTKBaseRequest *request) {

NSDictionary* dic = [request.responseString JSONObject]; // request.responseString JSONString->NSDictionary

if (dic && ([[dic valueForKey:@"result"] integerValue] == 0))

{

weakSelf.personModel = [PersonModel objectWithKeyValues:[dic valueForKey:@"data"]]; //personModel为PersonModel对象，跟后台约定data字段为字典

//weakSelf.personModelArr = [PersonModel objectArrayWithKeyValuesArray:[dic valueForKey:@"data"]]; //personModelArr为PersonModel数组，跟后台约定data字段为字典数组

}

}