fpjsondataset: what changed
Revision 0 to 1. Removed lines have a minus sign; added lines have a plus sign.
Title: fpjsondataset
| Old | New | Line | |
|---|---|---|---|
| 1 | + | **fpjsondataset** is an fcl-db unit containing a dataset class for accessing JSON data as simple table structures. | |
| 2 | + | ||
| 3 | + | ## TJSONDataSet | |
| 4 | + | ||
| 5 | + | TJSONDataSet is a dataset class for using JSON arrays for data handling. | |
| 6 | + | ||
| 7 | + | > **Note:** TJSONDataSet is included in Free Pascal but not visible in Lazarus' component palette. | |
| 8 | + | ||
| 9 | + | ### Example | |
| 10 | + | ||
| 11 | + | 1. Create a new application project | |
| 12 | + | 2. Place a DB Grid on the form (DBGrid1) | |
| 13 | + | 3. Place a DataSource on the form (DataSource1) | |
| 14 | + | 4. Connect DBGrid1.Datasource with DataSource1 | |
| 15 | + | 5. Create a JSON dataset via code | |
| 16 | + | ||
| 17 | + | ``` pascal | |
| 18 | + | unit Unit1; | |
| 19 | + | ||
| 20 | + | {$mode objfpc}{$H+} | |
| 21 | + | ||
| 22 | + | interface | |
| 23 | + | ||
| 24 | + | uses | |
| 25 | + | Classes, SysUtils, Forms, Controls, Graphics, Dialogs, DBCtrls, DBGrids, DB, | |
| 26 | + | fpjson, fpjsondataset; | |
| 27 | + | ||
| 28 | + | type | |
| 29 | + | ||
| 30 | + | TForm1 = class(TForm) | |
| 31 | + | DataSource1: TDataSource; | |
| 32 | + | DBGrid1: TDBGrid; | |
| 33 | + | procedure FormCreate(Sender: TObject); | |
| 34 | + | private | |
| 35 | + | JSONDataSet: TJSONDataSet; | |
| 36 | + | end; | |
| 37 | + | ||
| 38 | + | var | |
| 39 | + | Form1: TForm1; | |
| 40 | + | ||
| 41 | + | const | |
| 42 | + | // this is the sample JSON data used in the demo | |
| 43 | + | JSON_STRING = '[' | |
| 44 | + | +'{"Author ID":"409-56-7008","Last Name":"Bennet","First Name":"Abraham","Active": False},' | |
| 45 | + | +'{"Author ID":"213-46-8915","Last Name":"Green","First Name":"Marjorie","Active": True}' | |
| 46 | + | +']'; | |
| 47 | + | ||
| 48 | + | implementation | |
| 49 | + | ||
| 50 | + | {$R *.lfm} | |
| 51 | + | ||
| 52 | + | procedure TForm1.FormCreate(Sender: TObject); | |
| 53 | + | var | |
| 54 | + | data: TJSONArray; | |
| 55 | + | begin | |
| 56 | + | // parse the JSON string | |
| 57 | + | data := GetJSON(JSON_STRING) as TJSONArray; | |
| 58 | + | // create a new TJSONDataSet | |
| 59 | + | JSONDataSet := TJSONDataSet.Create(Self); | |
| 60 | + | // you'll need to create the FieldDefs manually | |
| 61 | + | // ftString requires a length specified | |
| 62 | + | JSONDataSet.FieldDefs.Add('Author ID', ftString, 11, True); | |
| 63 | + | JSONDataSet.FieldDefs.Add('Last Name', ftString, 40); | |
| 64 | + | JSONDataSet.FieldDefs.Add('First Name', ftString, 20); | |
| 65 | + | JSONDataSet.FieldDefs.Add('Active', ftBoolean); | |
| 66 | + | // set OwnsData to True, and the JSON data will be destroyed when the dataset is destroyed | |
| 67 | + | JSONDataSet.OwnsData := True; | |
| 68 | + | // the JSON data is an array of objects | |
| 69 | + | JSONDataSet.RowType := rtJSONObject; | |
| 70 | + | // assign the JSON data to the dataset | |
| 71 | + | JSONDataSet.Rows := data; | |
| 72 | + | // activate the dataset | |
| 73 | + | JSONDataSet.Active := True; | |
| 74 | + | // assign the dataset to the datasource | |
| 75 | + | DataSource1.DataSet := JSONDataSet; | |
| 76 | + | end; | |
| 77 | + | ||
| 78 | + | end. | |
| 79 | + | ||
| 80 | + | ``` | |
| 81 | + | ||
| 82 | + | --- | |
| 83 | + | *From the Free Pascal wiki, page "fpjsondataset", as it stood on 2021-04-01 after a change by Socke, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).* | |
| 84 | + | Category: Databases | |
| 85 | + | Category: FCL |