json字符串转换

1.json字符串转字典或数组
方法：+ (id)JSONObjectWithData:(NSData)dataoptions:(NSJSONReadingOptions)opterror:(NSError _Nullable *)error

``` javascript

NSString *jsonStr;

NSData*jsonData = [jsonStrdataUsingEncoding:NSUTF8StringEncoding];

NSError*error;

NSDictionary*dic = [NSJSONSerialization JSONObjectWithData:jsonDataoptions:NSJSONReadingMutableContainers error:&error];

2.数组或者字典转换为json字符串

方法：+ (NSData)dataWithJSONObject:(id)objoptions:(NSJSONWritingOptions)opterror:(NSError _Nullable *)error

NSData *jsonData =[NSJSONSerialization dataWithJSONObject:dicoptions:(NSJSONWritingOptions)opterror:&error];