Table of Contents

Import & export (JSON)

Load a JSON file, stream, or string directly into the grid. Map the JSON object structure to grid columns by supplying the key names that contain your row array and column values.

Overview

JSON import is built into the core grid. There is no separate JSON export (use CSV for round-trip data transfer); the JSON import is designed for loading data from REST APIs or configuration files.

Operation Method
Load from file Grid.LoadFromJSONData(FileName)
Load from stream Grid.LoadFromJSONStreamData(Stream)
Load from string Grid.LoadFromJSONTextData(Text)

All three share the same optional mapping parameters:

Parameter Type Purpose
ARowDataName string Key whose value is the JSON array of rows. Pass '' if the root is already an array.
AColumnDataName string Key inside each row object whose value is the array of column values. Pass '' for flat row objects.
AColumnNames TTMSFNCDataGridDataJSONNamesArray Maps JSON property names to specific column indices.

Step by step

Flat array of objects

The most common shape — a JSON array at the root, each element an object with one property per column:

[
  { "id": 1, "name": "Alice", "country": "DE" },
  { "id": 2, "name": "Bob",   "country": "US" }
]

Grid.ColumnCount   := 3;
Grid.FixedRowCount := 1;
Grid.Cells[0, 0] := 'ID';
Grid.Cells[1, 0] := 'Name';
Grid.Cells[2, 0] := 'Country';

// Map JSON keys to columns in order
Grid.LoadFromJSONTextData(JsonText, '', '',
  ['id', 'name', 'country']);     // AColumnNames: key → column order

AColumnNames is an array of property name strings; their position in the array corresponds to the grid column index.

Nested structure with a wrapper key

When the JSON has a wrapper object with a named array inside:

{
  "data": [
    { "id": 1, "name": "Alice" },
    { "id": 2, "name": "Bob"   }
  ]
}

Grid.LoadFromJSONData('customers.json', 'data', '',
  ['id', 'name']);     // ARowDataName = 'data'

Array of arrays (columnar data)

When each row is a JSON array of values rather than an object:

{
  "rows": [
    { "cols": [1, "Alice", "DE"] },
    { "cols": [2, "Bob",   "US"] }
  ]
}

Grid.LoadFromJSONData('data.json',
  'rows',              // ARowDataName
  'cols',              // AColumnDataName — key inside each row object
  nil);                // no name mapping needed; columns are positional

Load from a stream (REST response)

var Response := TMemoryStream.Create;
try
  HttpClient.Get('https://api.example.com/data', Response);
  Response.Position := 0;
  Grid.LoadFromJSONStreamData(Response, '', '', ['id', 'name', 'value']);
finally
  Response.Free;
end;

Load from a string (TRestResponse)

Grid.LoadFromJSONTextData(RESTResponse1.Content, 'data', '',
  ['id', 'name', 'value']);

Transform values during import

OnLoadCellData fires for every cell as it is populated from the JSON, letting you convert or replace the parsed value before it is stored in the grid:

procedure TForm1.GridLoadCellData(Sender: TObject;
  AColumn, ARow: Integer;
  var AValue: TTMSFNCDataGridCellValue);
begin
  // JSON may deliver numbers as strings; convert to TDateTime where needed
  if AColumn = DateColumn then
  begin
    var D: TDateTime;
    if TryStrToDateTime(AValue.AsString, D) then
      AValue := TValue.From<TDateTime>(D);
  end;
end;
  • Grid.LoadFromJSONData(AFileName, ARowDataName, AColumnDataName, AColumnNames)
  • Grid.LoadFromJSONStreamData(AStream, ARowDataName, AColumnDataName, AColumnNames)
  • Grid.LoadFromJSONTextData(AText, ARowDataName, AColumnDataName, AColumnNames)
  • TTMSFNCDataGridDataJSONNamesArray — TArray<string> of JSON key names mapped to column indices
  • OnLoadCellData — transform a cell value as it is read from the JSON source.

See also