JSON数据使用详解

// 如果数组或者字典中存储了  NSString, NSNumber, NSArray, NSDictionary, or NSNull 之外的其他对象,就不能直接保存成文件了.也不能序列化成 JSON 数据.
    NSDictionary *dict = @{@"name" : @"me", @"do" : @"something", @"with" : @"her", @"address" : @"home"};
    
    // 1.判断当前对象是否能够转换成JSON数据.
    // YES if obj can be converted to JSON data, otherwise NO
    BOOL isYes = [NSJSONSerialization isValidJSONObject:dict];
    
    if (isYes) {
        NSLog(@"可以转换");
        
        /* JSON data for obj, or nil if an internal error occurs. The resulting data is a encoded in UTF-8.
         */
        NSData *jsOnData= [NSJSONSerialization dataWithJSONObject:dict options:0 error:NULL];
        
        /*
         Writes the bytes in the receiver to the file specified by a given path.
         YES if the operation succeeds, otherwise NO
         */
        // 将JSON数据写成文件
        // 文件添加后缀名: 告诉别人当前文件的类型.
        // 注意: AFN是通过文件类型来确定数据类型的!如果不添加类型,有可能识别不了! 自己最好添加文件类型.
        [jsonData writeToFile:@"/Users/SunnyBoy/Sites/JSON_XML/dict.json" atomically:YES];
        
        NSLog(@"%@", [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]);
        
    } else {
        
        NSLog(@"JSON数据生成失败，请检查数据格式");
        
    }

　　 NSArray *array = @[@"qn", @18, @"ya", @"wj"];
    
    BOOL isYes = [NSJSONSerialization isValidJSONObject:array];
    
    if (isYes) {
        NSLog(@"可以转换");
        
        NSData *data = [NSJSONSerialization dataWithJSONObject:array options:0 error:NULL];
        
        [data writeToFile:@"/Users/SunnyBoy/Sites/JSON_XML/base" atomically:YES];
    
    } else {
        
        NSLog(@"JSON数据生成失败，请检查数据格式");
        
    }

//使用TouchJson来解析北京的天气
//获取API接口
NSURL *url = [NSURL URLWithString:@"http://m.weather.com.cn/data/101010100.html"];

//定义一个NSError对象，用于捕获错误信息
NSError *error;
NSString *jsOnString= [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];

NSLog(@"jsonString--->%@",jsonString);

//将解析得到的内容存放字典中，编码格式为UTF8，防止取值的时候发生乱码
NSDictionary *rootDic = [[CJSONDeserializer deserializer] deserialize:[jsonString dataUsingEncoding:NSUTF8StringEncoding] error:&error];

//因为返回的Json文件有两层，去第二层内容放到字典中去
NSDictionary *weatherInfo = [rootDic objectForKey:@"weatherinfo"];
NSLog(@"weatherInfo--->%@",weatherInfo);

//取值打印
NSLog(@"%@",[NSString stringWithFormat:@"今天是 %@  %@  %@  的天气状况是：%@  %@ ",[weatherInfo objectForKey:@"date_y"],[weatherInfo objectForKey:@"week"],[weatherInfo objectForKey:@"city"], [weatherInfo objectForKey:@"weather1"], [weatherInfo objectForKey:@"temp1"]]);

//使用SBJson解析北京的天气
NSURL *url = [NSURL URLWithString:@"http://www.weather.com.cn/adat/sk/101010100.html"];

NSError *error = nil;

NSString *jsOnString= [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];

SBJsonParser *parser = [[SBJsonParser alloc] init];

NSDictionary *rootDic = [parser objectWithString:jsonString error:&error];

NSDictionary *weatherInfo = [rootDic objectForKey:@"weatherinfo"];

NSLog(@"%@", [NSString stringWithFormat:@"今天是 %@  %@  %@  的天气状况是：%@  %@ ",[weatherInfo objectForKey:@"date_y"],[weatherInfo objectForKey:@"week"],[weatherInfo objectForKey:@"city"], [weatherInfo objectForKey:@"weather1"], [weatherInfo objectForKey:@"temp1"]]);

// 从中国天气预报网请求数据
    NSURL *url = [ NSURL URLWithString:@"http://www.weather.com.cn/adat/sk/101010100.html"];
    
    // 创建请求
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    
    [[[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        
        // 在网络完成的 Block 回调中,要增加错误机制.
        // 失败机制处理: 错误的状态码!
        
        // 最简单的错误处理机制:
        if (data && !error) {
            
            // JSON格式转换成字典，IOS5中自带解析类NSJSONSerialization从response中解析出数据放到字典中
            id obj = [NSJSONSerialization JSONObjectWithData:data options:0 error:NULL];
            
            NSDictionary *dict = obj[@"weatherinfo"];
            
            NSLog(@"%@---%@", dict, dict[@"city"]);
        }
        
    }] resume];

//如果json是“单层”的，即value都是字符串、数字，可以使用objectFromJSONString
NSString *json1 = @"{\"a\":123, \"b\":\"abc\"}";
NSLog(@"json1:%@",json1);

NSDictionary *data1 = [json1 objectFromJSONString];
NSLog(@"json1.a:%@",[data1 objectForKey:@"a"]);
NSLog(@"json1.b:%@",[data1 objectForKey:@"b"]);

//如果json有嵌套，即value里有array、object，如果再使用objectFromJSONString，程序可能会报错（测试结果表明：使用由网络或得到的php/json_encode生成的json时会报错，但使用NSString定义的json字符串时，解析成功），最好使用objectFromJSONStringWithParseOptions：
NSString *json2 = @"{\"a\":123, \"b\":\"abc\", \"c\":[456, \"hello\"], \"d\":{\"name\":\"张三\", \"age\":\"32\"}}";
NSLog(@"json2:%@", json2);

NSDictionary *data2 = [json2 objectFromJSONStringWithParseOptions:JKParseOptionLooseUnicode];
NSLog(@"json2.c:%@", [data2 objectForKey:@"c"]);
NSLog(@"json2.d:%@", [data2 objectForKey:@"d"]);