如何在 Delphi XE2 中解析嵌套的 JSON 对象? [英] How to parse nested JSON object in Delphi XE2?

问题描述

我是 JSON 的新手，我手头上有这个项目，需要我解析 JSON 并在 ListView 中显示其中的一些内容.问题是我现在阅读的文档处理包含 JSON 数组的 JSON 对象，而我的案例涉及处理嵌套对象.简而言之，总结如下:我将 Delphi XE2 与 DBXJSON 结合使用.我将一些值发布到服务器，它用一个看起来像这样的 JSON 对象回复:

I'm new to JSON and I have this project on my hands that require me to parse a JSON and display some of its contents in a ListView. The problem is that the documentation I've read by now dealt with JSON objects containing JSON arrays, while my case involves dealing with nested objects. To cut the story short, here's the summary: I'm using Delphi XE2 with DBXJSON. I post some values to a server and it replies with a JSON object that looks like that:

    {
    "products": {
        "Men's Sneakers": {
            "instock": false,
            "size": "423",
            "manufacturer": "Adidas",
            "lastcheck": "20120529"
        },
        "Purse": {
            "instock": true,
            "size": "not applicable",
            "manufacturer": "Prada",
            "lastcheck": "20120528"
        },
        "Men's Hood": {
            "instock": false,
            "size": "M",
            "manufacturer": "Generic",
            "lastcheck": "20120529"
       }
    },
   "total": 41,
   "available": 30
}

我想要实现的是将每个项目(即钱包)解析并添加为列表视图中的标题，以及一个子项目(制造商).我创建了一个以 JSON 字符串作为参数的过程，创建了 JSON 对象，但我不知道如何进一步解析嵌套对象.

What I wanted to achieve was to have each item (i.e. Purse) parsed and added as caption in a listview, along with one subitem (manufacturer). I created a procedure that takes the JSON string as argument, created the JSON object, but I don't know how to parse the nested objects any further.

procedure TForm1.ParseString(const AString: string);
var
  json          : TJSONObject;
  jPair         : TJSONPair;
  jValue        : TJSONValue;
  jcValue       : TJSONValue;
  l,i           : Integer;
begin
    json    := TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes(AString),0) as TJSONObject;
  try
    //get the pair to evaluate in this case the index is 1
    jPair   := json.Get(1); 
        {further process the nested objects and adding them to the listview}
  finally
     json.Free;
  end;
end;

任何建议将不胜感激.花了很多时间试图在 Delphi 中了解 JSON 的来龙去脉，但无济于事.

Any suggestions would be highly appreciated. Lost quite some time trying to get the ins and outs of JSON in Delphi with no avail.

谢谢，斯芬克斯

推荐答案

试试这个示例

{$APPTYPE CONSOLE}

{$R *.res}

uses
  DBXJSON,
  System.SysUtils;


Const
StrJson=
'{'+
'    "products": {'+
'        "Men''s Sneakers": {'+
'            "instock": false,'+
'            "size": "423",'+
'            "manufacturer": "Adidas",'+
'            "lastcheck": "20120529"'+
'        },'+
'        "Purse": {'+
'            "instock": true,'+
'            "size": "not applicable",'+
'            "manufacturer": "Prada",'+
'            "lastcheck": "20120528"'+
'        },'+
'        "Men''s Hood": {'+
'            "instock": false,'+
'            "size": "M",'+
'            "manufacturer": "Generic",'+
'            "lastcheck": "20120529"'+
'        }'+
'    },'+
'    "total": 41,'+
'    "available": 30'+
'}';

procedure ParseJson;
var
  LJsonObj  : TJSONObject;
  LJPair    : TJSONPair;
  LProducts : TJSONValue;
  LProduct  : TJSONValue;
  LItem     : TJSONValue;
  LIndex    : Integer;
  LSize     : Integer;
begin
    LJsonObj    := TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes(StrJson),0) as TJSONObject;
  try
     LProducts:=LJsonObj.Get('products').JsonValue;
     LSize:=TJSONArray(LProducts).Size;
     for LIndex:=0 to LSize-1 do
     begin
      LProduct := TJSONArray(LProducts).Get(LIndex);
      LJPair   := TJSONPair(LProduct);
      Writeln(Format('Product Name %s',[LJPair.JsonString.Value]));
        for LItem in TJSONArray(LJPair.JsonValue) do
        begin
           if TJSONPair(LItem).JsonValue is TJSONFalse then
            Writeln(Format('  %s : %s',[TJSONPair(LItem).JsonString.Value, 'false']))
           else
           if TJSONPair(LItem).JsonValue is TJSONTrue then
            Writeln(Format('  %s : %s',[TJSONPair(LItem).JsonString.Value, 'true']))
           else
            Writeln(Format('  %s : %s',[TJSONPair(LItem).JsonString.Value, TJSONPair(LItem).JsonValue.Value]));
        end;
     end;
  finally
     LJsonObj.Free;
  end;
end;

begin
  try
    ParseJson;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
  Readln;
end.

这将返回

Product Name Men's Sneakers
  instock : false
  size : 423
  manufacturer : Adidas
  lastcheck : 20120529
Product Name Purse
  instock : true
  size : not applicable
  manufacturer : Prada
  lastcheck : 20120528
Product Name Men's Hood
  instock : false
  size : M
  manufacturer : Generic
  lastcheck : 20120529

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