plist文件读取写入
https://www.jianshu.com/p/33974a2928b7

json保存为plist

##--------先在项目创建  footData.plist 文件，放到document 里面，再运行
- (void)saveData:(NSDictionary *)dic
{
    NSDictionary *cityDic = @{ @"data":dic[@"data"]};
    
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    
    NSString *plistPath1= [paths objectAtIndex:0];
    
    NSLog(@"------------------%@",plistPath1);  //得到完整的路径名
    
    NSString *fileName = [plistPath1 stringByAppendingPathComponent:@"footData.plist"];
    
    NSFileManager *fm = [NSFileManager defaultManager];
    
    if ([fm createFileAtPath:fileName contents:nil attributes:nil] ==YES)
    {
        
        [cityDic writeToFile:fileName atomically:YES];
        
        NSLog(@"文件写入完成");
    }
     NSLog(@"------------------%@",dic[@"data"]);

}