IOS 返回JSON数据中存在NULL的解决办法

#import <Foundation/Foundation.h>

@interface NSDictionary (SetNilStr)
+(id)changeType:(id)myObj;
@end

#import "NSDictionary+SetNilStr.h"

@implementation NSDictionary (SetNilStr)

//将NSDictionary中的Null类型的项目转化成@""
+(NSDictionary *)nullDic:(NSDictionary *)myDic
{
NSArray *keyArr = [myDic allKeys];
NSMutableDictionary *resDic = [[NSMutableDictionary alloc]init];
for (int i = 0; i < keyArr.count; i ++)
{
id obj = [myDic objectForKey:keyArr[i]];

obj = [self changeType:obj];

[resDic setObject:obj forKey:keyArr[i]];
}
return resDic;
}

//将NSArray中的Null类型的项目转化成@""
+(NSArray *)nullArr:(NSArray *)myArr
{
NSMutableArray *resArr = [[NSMutableArray alloc] init];
for (int i = 0; i < myArr.count; i ++)
{
id obj = myArr[i];

obj = [self changeType:obj];

[resArr addObject:obj];
}
return resArr;
}

//将NSString类型的原路返回
+(NSString *)stringToString:(NSString *)string
{
return string;
}

//将Null类型的项目转化成@""
+(NSString *)nullToString
{
return @"";
}

//主要方法
//类型识别:将所有的NSNull类型转化成@""
+(id)changeType:(id)myObj
{
if ([myObj isKindOfClass:[NSDictionary class]])
{
return [self nullDic:myObj];
}
else if([myObj isKindOfClass:[NSArray class]])
{
return [self nullArr:myObj];
}
else if([myObj isKindOfClass:[NSString class]])
{
return [self stringToString:myObj];
}
else if([myObj isKindOfClass:[NSNull class]])
{
return [self nullToString];
}
else
{
return myObj;
}
}

@end

//json表示获取到的带有NULL对象的json数据
NSDictionary *newDict = [NSDictionary changeType:json];