使用Delphi 7解析JSON

Question

使用Delphi 7解析JSON

7

我有一个JSON文件，需要解析并提取一些值。

样例如下：

[
  {
    "period": "2016-06-07 - 2016-06-14",
    "range": "2016-06-07..2016-06-14",
    "items": [
      {
        "region_name": "Canterbury/Otago",
        "region_id": 12,
        "average_cover": 2099,
        "average_growth": 16,
        "reading_count": 3
      },
      {
        "region_name": "Southland",
        "region_id": 14,
        "average_cover": 2068,
        "average_growth": 3,
        "reading_count": 1
      },
      {
        "region_name": "Wairarapa \u0026 Hawkes Bay",
        "region_id": 10,
        "average_cover": 2195,
        "average_growth": 20,
        "reading_count": 2
      }
    ]
  },
  {
    "period": "2016-05-31 - 2016-06-07",
    "range": "2016-05-31..2016-06-07",
    "items": [
      {
        "region_name": "Canterbury/Otago",
        "region_id": 12,
        "average_cover": 2126,
        "average_growth": 17,
        "reading_count": 5
      },
      {
        "region_name": "Southland",
        "region_id": 14,
        "average_cover": 2181,
        "average_growth": 10,
        "reading_count": 2
      }
    ]
  },
  {
    "period": "2016-05-24 - 2016-05-31",
    "range": "2016-05-24..2016-05-31",
    "items": [
      {
        "region_name": "Canterbury/Otago",
        "region_id": 12,
        "average_cover": 2139,
        "average_growth": 28,
        "reading_count": 6
      },
      {
        "region_name": "Central Plateau",
        "region_id": 6,
        "average_cover": 2400,
        "average_growth": 38,
        "reading_count": 1
      },
      {
        "region_name": "Wairarapa \u0026 Hawkes Bay",
        "region_id": 10,
        "average_cover": 2254,
        "average_growth": 27,
        "reading_count": 2
      }
    ]
  },
  {
    "period": "2016-05-18 - 2016-05-25",
    "range": "2016-05-18..2016-05-25",
    "items": [
      {
        "region_name": "Canterbury/Otago",
        "region_id": 12,
        "average_cover": 2183,
        "average_growth": 39,
        "reading_count": 6
      },
      {
        "region_name": "Manawatu",
        "region_id": 9,
        "average_cover": 2315,
        "average_growth": 42,
        "reading_count": 1
      },
      {
        "region_name": "Wairarapa \u0026 Hawkes Bay",
        "region_id": 10,
        "average_cover": 2228,
        "average_growth": 29,
        "reading_count": 2
      }
    ]
  },
  {
    "period": "2016-05-10 - 2016-05-17",
    "range": "2016-05-10..2016-05-17",
    "items": [
      {
        "region_name": "Canterbury/Otago",
        "region_id": 12,
        "average_cover": 2251,
        "average_growth": 40,
        "reading_count": 8
      },
      {
        "region_name": "Otago",
        "region_id": 13,
        "average_cover": 2595,
        "average_growth": 26,
        "reading_count": 1
      },
      {
        "region_name": "Southland",
        "region_id": 14,
        "average_cover": 2526,
        "average_growth": 49,
        "reading_count": 2
      },
      {
        "region_name": "Waikato",
        "region_id": 4,
        "average_cover": 2484,
        "average_growth": 60,
        "reading_count": 1
      },
      {
        "region_name": "Wairarapa \u0026 Hawkes Bay",
        "region_id": 10,
        "average_cover": 2201,
        "average_growth": 34,
        "reading_count": 2
      }
    ]
  }
]

我需要提取的项目是region_id，average_cover和average_growth。

我已经成功地从第一个items数组中提取了值，但我的样本JSON文件包含4个items数组，我似乎只能从第一个items元素中提取值。

我一直在使用ulkJSON.pas库，我的Delphi代码如下，将值发送到表单上的TMemo：

var 
  js: TlkJSONBase;
  Items: TlkJSONbase;
  I: Integer;
  lHTTP: TIdHTTP;
  sJSON: String;      
begin
  sJSON :=  // as per sample JSON text in question
  js := TlkJSON.ParseText(sJSON);
  Items := js.Field['items'];
  for I := 0 to Pred(Items.Count) do begin
    Memo1.Lines.Add(VarToStr(Items.Child[I].Field['region_id'].Value));
    Memo1.Lines.Add(VarToStr(Items.Child[I].Field['average_cover'].Value));
    Memo1.Lines.Add(VarToStr(Items.Child[I].Field['average_growth'].Value));
  end;
end;

- DaveMc

我尝试为您格式化JSON代码，但它显然不是有效的JSON。编辑实际上，您忘记包括开放/关闭数组括号（[]）。但是，即使有了这个，无论如何，我都看不出您如何按照您编写的代码读取items对象。 - Jerry Dodge

我重新格式化了JSON，使数组更清晰。但是，代码与所示的JSON不匹配。 - Remy Lebeau

1个回答

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- Remy Lebeau · Accepted Answer

您没有考虑到顶级数组。这段代码适用于所示的JSON：

var 
  sJSON: String;      
  js, Items, Item: TlkJSONBase;
  I, J: Integer;
begin
  sJSON :=  // as per sample JSON text in question
  js := TlkJSON.ParseText(sJSON);
  for I := 0 to Pred(js.Count) do
  begin
    Items := js.Child[I].Field['items'];
    for J := 0 to Pred(Items.Count) do begin
      Item := Items.Child[J];
      Memo1.Lines.Add(VarToStr(Item.Field['region_id'].Value));
      Memo1.Lines.Add(VarToStr(Item.Field['average_cover'].Value));
      Memo1.Lines.Add(VarToStr(Item.Field['average_growth'].Value));
    end;
  end;
end;