json數據解析

json的概念

JSON(JavaScript Object Notation)是一種輕量級的數據交換格式。
在實際開發中經常使用JSON來獲取服務器上的數據，并通過解析json數據獲取我們想要的數據

iOS開發使用 NSJSONSerialization（序列化）類解析json數據
NSJSONSerialization提供了Json數據封包、Json數據解析

NSJSONSerialization將JSON數據轉換為NSDictionary或NSArray
解包方法，將NSDictionary、NSArray對象轉換為JSON數據（可以通過調用isValidJSONObject來判斷NSDictionary、NSArray對象是否可以轉換為JSON數 據）封包

json數據封包

   NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:@"value1",@"key1",@"value2",@"key2",@"value3",@"key3", nil];

      // isValidJSONObject判斷對象是否可以構建成json對象
      if ([NSJSONSerialization isValidJSONObject:dic]){
          NSError *error;

          // 創造一個json從Data, NSJSONWritingPrettyPrinted指定的JSON數據產的空白，使輸出更具可讀性。
          NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dic options:NSJSONWritingPrettyPrinted error:&error];

          NSString *json =[[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
          NSLog(@"json data:%@",json);
      }

json數據解析

  NSError *error;
  //加載一個NSURL對象
  NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://m.weather.com.cn/data/101120101.html"]];

  //將請求的url數據放到NSData對象中
  NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];  
  
//iOS自帶解析類NSJSONSerialization從response中解析出數據放到字典中
  NSDictionary *weatherDic = [NSJSONSerialization JSONObjectWithData:response options:NSJSONReadingMutableLeaves error:&error];

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

  NSString *text = [NSString stringWithFormat:@"今天是 %@  %@  %@  的天氣狀況是：%@  %@ ",[weatherInfo objectForKey:@"date_y"],[weatherInfo objectForKey:@"week"],[weatherInfo objectForKey:@"city"], [weatherInfo objectForKey:@"weather1"], [weatherInfo objectForKey:@"temp1"]];    NSLog(@"weatherInfo：%@", text );

json解析過程示例

  NSError *error;
//加載一個NSURL對象
NSURLRequest\*request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://m.weather.com.cn/data/101180601.html"]];

//將請求的url數據放到NSData對象中
NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];

//iOS自帶解析類NSJSONSerialization從response中解析出數據放到字典中
NSDictionary *weatherDic = [NSJSONSerialization JSONObjectWithData:response options:NSJSONReadingMutableLeaves error:&error];

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

txtView.text = [NSString stringWithFormat:@"今天是 %@ %@ %@ 的天氣狀況是：%@ %@ ",[weatherInfo objectForKey:@"date_y"],[weatherInfo objectForKey:@"week"],[weatherInfo objectForKey:@"city"], [weatherInfo objectForKey:@"weather1"], [weatherInfo objectForKey:@"temp1"]];

NSLog(@"weatherInfo字典里面的內容為---%@", weatherDic );