Generate JSON array with LKJSON in Delphi 7

Question

I want to produce something like this:

{
  "nrVendas": 2, 
  "totalVendas": 100.0, 
  "vendas": [ 
    {
      "nsuOrigem": "1",
      "data": "2014-03-14",
      "nrParcelas": 1,
      "valor": 50,
      "parcelas": [
        {
          "numero": 1,
          "valor": 50
        }
      ]
    }, 
    {
      "nsuOrigem": "2",
      "data": "2014-03-14",
      "nrParcelas": 1,
      "valor": 50,
      "parcelas": [
        {
          "numero": 1,
          "valor": 50
        }
      ]
    }
  ]
}

I'm trying it this way:

js3 := TlkJSONobject.Create;
js3.Add('numero', '1');
js3.Add('valor', '50');

js32 :=  TlkJSONobject.Create;
js32.Add('numero', '1');
js32.Add('valor', '100');

js2 := TlkJSONobject.Create;
js2.Add('nsuOrigem', '1');
js2.Add('data', '2014-02-02');
js2.Add('nrParcelas', 1);
js2.Add('valor', 50);
js2.Add('parcelas', js3);

js2.Add('nsuOrigem', '2');
js2.Add('data', '2014-02-02');
js2.Add('nrParcelas', 1);
js2.Add('valor', 50);
js2.Add('parcelas', js32);

js0 := TlkJSONobject.Create;
js0.Add('numeroVendas', 2);
js0.Add('totalVendas', 100.0);
js0.Add('vendas', js2);

i := 0;
s := GenerateReadableText(js0, i);

Memo2.Lines.Add(s);

But I'm receiving this instead:

{
  "numeroVendas": 2,
  "totalVendas": 100,
  "vendas": {
    "nsuOrigem": "1",
    "data": "2014-02-02",
    "nrParcelas": 1,
    "valor": 50,
    "parcelas": {
      "numero": "1",
      "valor": "50"
    },
    "nsuOrigem": "2",
    "data": "2014-02-02",
    "nrParcelas": 1,
    "valor": 50,
    "parcelas": {
      "numero": "1",
      "valor": "100"
    }
  }
}

Then I try to validade this JSON, but i received this error:

SyntaxError: Duplicate key 'nsuOrigem' on line 13

I think I need to use an array on the fields inside vendas, but I searched in all of the documentation and more, but I can't find anything that can help me.

Well, you aren't attempting to create an array, so why would you expect one? Read the code again. Read the examples for array creation for this library. Don't make the classic mistake of trying to write your final code without first learning the library using simple examples. — David Heffernan, May 10 '17 at 02:03

score 3 · Accepted Answer · answered May 10 '17 at 05:30

You are not creating any arrays at all. vendas and parcelas are both an array of objects, but you are creating them as through they are single objects instead.

You are also creating a few of the JSON values as strings instead of as numbers.

Use the TlkJSONlist class to create arrays, eg:

js4_1 := TlkJSONobject.Create;
js4_1.Add('numero', 1);
js4_1.Add('valor', 50);

js4_2 := TlkJSONobject.Create;
js4_2.Add('numero', 1);
js4_2.Add('valor', 100);

js3_1 := TlkSONlist.Create;
js3_1.Add(js4_1);

js3_2 := TlkSONlist.Create;
js3_2.Add(js4_2);

js2_1 := TlkJSONobject.Create;
js2_1.Add('nsuOrigem', '1');
js2_1.Add('data', '2014-02-02');
js2_1.Add('nrParcelas', 1);
js2_1.Add('valor', 50);
js2_1.Add('parcelas', js3_1);

js2_2.Add('nsuOrigem', '2');
js2_2.Add('data', '2014-02-02');
js2_2.Add('nrParcelas', 1);
js2_2.Add('valor', 50);
js2_2.Add('parcelas', js3_2);

js1 := TlkJSONlist.Create;
js1.Add(js2_1);
js1.Add(js2_2);

js0 := TlkJSONobject.Create;
js0.Add('numeroVendas', 2);
js0.Add('totalVendas', 100.0);
js0.Add('vendas', js1);

i := 0;
s := GenerateReadableText(js0, i);

Memo2.Lines.Add(s);

But please, give your variables more meaningful names! And change the order of your class constructions, it will make the code much easier to read and follow, eg:

root := TlkJSONobject.Create;
root.Add('numeroVendas', 2);
root.Add('totalVendas', 100.0);
vendas := TlkJSONList.Create;
root.Add('vendas', vendas);

venda := TlkJSONobject.Create;
vendas.Add(venda);
venda.Add('nsuOrigem', '1');
venda.Add('data', '2014-02-02');
venda.Add('nrParcelas', 1);
venda.Add('valor', 50);
parcelas := TlkJSONlist.Create;
venda.Add('parcelas', parcelas);

parcela := TlkJSONobject.Create;
parcelas.Add(parcela);
parcela.Add('numero', 1);
parcela.Add('valor', 50);

venda := TlkJSONobject.Create;
vendas.Add(venda);
venda.Add('nsuOrigem', '1');
venda.Add('data', '2014-02-02');
venda.Add('nrParcelas', 1);
venda.Add('valor', 50);
parcelas := TlkJSONlist.Create;
venda.Add('parcelas', parcelas);

parcela := TlkJSONobject.Create;
parcelas.Add(parcela);
parcela.Add('numero', 1);
parcela.Add('valor', 100);

i := 0;
s := GenerateReadableText(root, i);

Memo2.Lines.Add(s);

Generate JSON array with LKJSON in Delphi 7

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