How can you create JSON manually using Delphi with the Mormot library?

Question

I would like to generate JSON to represent complex object, manually (without any RTTI etc).

Can this be done using Mormot (and how)?

I have found the JSON Variant type, but that one does not seem to be capable of producing a complex JSON like the one here: Generate JSON array with LKJSON in Delphi 7

Of course I could use lkJSON like but since my project already uses Mormot, I would prefer to use the library already in use.

You don't need to use mormot for this, Delphi ships with a JSON library. — David Heffernan, Oct 09 '17 at 15:39
I was hoping that if Mormot supports this then it would be more efficient and faster then DBXJSON. — RM., Oct 09 '17 at 19:43
@DavidHeffernan I don't believe the JSON library ships with the PRO SKU (except if you add on the $500 FireDAC/database option). — alcalde, Oct 09 '17 at 19:57
I created [this](https://github.com/stijnsanders/jsonDoc#jsondoc) specifically to have a good concise notation to build JSON objects with Delphi syntax. It's heavily based on Variant's though... — Stijn Sanders, Oct 10 '17 at 12:13

Xalo · Accepted Answer · 2021-01-09T22:02:46.130

There are multiple ways in mORMot to generate any kind of json document.

You can find below one of them serializing the example you provided, IMHO more readable and easy to understand:

...
uses SynCommons;
...
var parcelas , venda , vendas , json : variant;
begin
  parcelas := _Obj(['numero',1,
                    'valor',50
                   ]);
  venda    := _Obj(['nsuOrigem','1',
                    'data','2014-03-14',
                    'nrParcelas',1,
                    'valor',50,
                    'parcelas' , _Arr([parcelas
                                      ])
                   ]);
  vendas := _Arr([venda]);
  venda := _Obj(['nsuOrigem','2',
                 'data','2014-03-14',
                 'nrParcelas',1,
                 'valor',50,
                 'parcelas' , _Arr([parcelas  //in this case this object is the same
                                   ])
                ]);
  TDocVariantData(vendas).AddItem(venda);
  json := _Obj(['nrVendas',2,
                'totalVendas',100.0,
                'vendas',vendas
               ]);
  //
  assert(json.nrVendas=2);
  assert(json.vendas._count=2);
  assert(json.vendas._(0).nsuOrigem='1');
  assert(json.vendas._(1).nsuOrigem='2');
  assert(json.vendas._(1).parcelas._(0).valor=50);
end;

This should work from Delphi 7 to 10.4. Please, find further details in the amazing documentation.

How can you create JSON manually using Delphi with the Mormot library?

1 Answers1