Parse Json again, complicated

[direktor05 2]

Hello,

 

How do I parse this Json:

 

{"result": [{
      "animals":
      [{
          "id":1,

         "name":

 

 

So.... I parse Json first:

jsonobject := TJsonObject.ParseJSONValue(RestResponse.Content) as TJsonObject;

 

Then I get to "animals":[{"id".... now here gets complicated. How do I parse further to get ID and name? Parse Json further or parse Json Array? Can someone help with some example code please?

[direktor05 2]

Full Json:

 

{"result":  [{
      "animals":
      [{
          "id":1,
          "name":"pig",

        } ]
    } ]
}

[ertank 27]

Hello,

 

Your "complete" json is not valid. You should edit your post and fix it.

 

There are more than one way to solve this. Below is an example with a lot of error checks.

type
  TAnimal = record
    id: Integer;
    name: string;
  end;
  TAnimalList = TArray<TAnimal>;
//-----------------------------------
implementation
//-----------------------------------
uses
  System.JSON,
  System.Generics.Collections;

const
  JsonString = '{"result":[{"animals":[{"id":1,"name":"pig"}]}]}';

function ParseAnimalsJson(const Json: string; out AnimalList: TAnimalList): Boolean;
var
  LTestJsonValue: TJSONValue;
  LJson: TJSONValue;
  LJsonArrayResult: TJSONArray;
  LJsonArrayAnimals: TJSONArray;
  I: Integer;
begin
  LTestJsonValue := TJSONObject.ParseJSONValue(Json, False, False);
  if LTestJsonValue = nil then
  begin
    Exit(False);
  end;

  try
    LJson := LTestJsonValue.FindValue('result');
    if LJson = nil then
      Exit(False);

    if not (LJson is TJSONArray) then
      Exit(False);

    LJsonArrayResult := LJson as TJSONArray;
    if LJsonArrayResult.Count = 0 then
      Exit(False);

    LJson := LJsonArrayResult[0].FindValue('animals');
    if LJson = nil then
      Exit(False);

    if not (LJson is TJSONArray) then
      Exit(False);

    LJsonArrayAnimals := LJson as TJSONArray;
    SetLength(AnimalList, LJsonArrayAnimals.Count);
    for I := 0 to LJsonArrayAnimals.Count-1 do
    begin
      LJson := LJsonArrayAnimals[I].FindValue('id');
      if LJson = nil then Exit(False);
      AnimalList[I].id := LJson.AsType<Integer>;

      LJson := LJsonArrayAnimals[I].FindValue('name');
      if LJson = nil then Exit(False);
      AnimalList[I].name := LJson.AsType<string>;
    end;
  finally
    LTestJsonValue.Free();
  end;
  Result := True;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  List: TAnimalList;
begin
  if ParseAnimalsJson(JsonString, List) then
  begin
    ShowMessage('Parse completed');
  end
  else
  begin
    ShowMessage('Parse failed!');
  end;
end;

 

Edited November 20, 2022 by ertank

[p-samuel 2]

Do you know about https://jsontodelphi.com/ website? If you are in a hurry then go there generate your classes dto's. Copy and past your json string and they will generate a dto boilerplate for you. The only problem is that this boilerplate uses generics and cannot be implemented in old versions of Delphi. Otherwise, check out Super Object in github project that is aimed for these cases.

Edited November 20, 2022 by p-samuel

[aehimself 396]

15 hours ago, direktor05 said:

Then I get to "animals":[{"id".... now here gets complicated. How do I parse further to get ID and name? Parse Json further or parse Json Array? Can someone help with some example code please?

Let's say you have a TJSONObject variable which holds the inmost object only (id and name) named innerjson:

if innerjson.GetValue('id') <> null then fid := (innerjson.GetValue('id') As TJSONNumber).AsLargeInt;
if innerjson.GetValue('name') <> null then fname := (innerjson.GetValue('name') As TJSONString).Value;

if you are sure that these will always be present, you can discard the nullcheck.

[David Schwartz 426]

If you create a class for this, then there's a method that can theoretically create an instance of it and fill it from a chunk of JSON data:
 

var data_obj := TJson.JsonToObject<TMyObj>( req.Response );

In this case, the JSON data would go into a class TMyObj, which is the type returned in data_obj.

 

I've used it for simple objects, but I'm not sure how it would handle lists and arrays. 

 

BTW, that JSON has an error in it -- a dangling comma

 

[Lars Fosdal 1792]

On 11/20/2022 at 1:00 PM, p-samuel said:

Do you know about https://jsontodelphi.com/ website?

That is interesting code.  How is the performance?

[Clément 148]

There are a few things to resolve before getting to "animal id".
This is just an example using Delphi 11, but older version should work too. (Might need to remove the inline variable).
This is how I would do it:
 

unit Unit94;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls,
  System.JSON;

type
  TForm94 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    const
      _JSON = ' {"result":  [{ "animals": [{ "id":1, "name":"pig" } ] } ] }';
  public
    { Public declarations }
  end;

var
  Form94: TForm94;

implementation

{$R *.dfm}

procedure TForm94.Button1Click(Sender: TObject);
var
  lJsResult : TJsonObject;
  lJsResultArray  : TJsonArray;
  lJsAnimals      : TJsonObject;
  lJsAnimalArray  : TJsonArray;
  lJsAnimal       : TJsonObject;

  lId : Integer;
  lname : String;
begin
   lJsResult := TJSONObject.ParseJSONValue(_JSON) as TJsonObject;
   try
     if lJsResult.TryGetValue<TJsonArray>('result', lJsResultArray) then begin

       for var r := 0 to lJsResultArray.Count-1 do begin
          lJsAnimals := lJsResultArray.Items[r] as TJsonObject;
          lJsAnimalArray := lJsAnimals.GetValue<TJsonArray>('animals');
          for var i := 0 to lJsAnimalArray.Count-1 do begin
             lJsAnimal := lJsAnimalArray.Items[i] as TJSONObject;
             if not lJsAnimal.TryGetValue<Integer>('id', lId ) then raise Exception.Create('No "ID" Field');
             if not lJsAnimal.TryGetValue<String>('name', lname) then raise Exception.Create('No "name" Field');

             // DO something with lId, and name

          end;
       end;
     end
   finally
     lJsResult.Free;
   end;

end;

 

[eddie Alves 0]

use this object, very simple:
https://github.com/hgourvest/superobject

 

Ex:

 

Function ...

var

  jsonPedido            : ISuperObject;

begin

 jsonPedido := SO(aPedido);

  if jsonPedido.Count > 0 then
  begin
    idPedido        := jsonPedido.S['codigo'];
    merchanId       := IntToStr(jsonPedido.I['idLoja']);
    totalPrice      := jsonPedido.F['valorCorrigido'];
    pedidoCreatAt   := jsonPedido.D['data'];
    idContato       := IntToStr(jsonPedido.O['cliente'].I['id']);
  end;

end;

Edited November 21, 2022 by eddie Alves