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DocsChoose and clear a date
McBasic™ 0.7.881 · Build 881 · 5 min read
Hands-on tutorial · Input & events

Choose and clear a date

Distinguish a selected date from a cleared value.

1 Form / control designs1 complete BASIC filesGuided sample project
Download complete projectComplete event code

A cleared picker is not the same as today. Keep the date selection and the output label in sync from Change, and use the clear action in the sample to exercise the empty case. Store a date as a date, not as a locale-dependent label.

Step 1Prepare a safe practice project#

Extract the archive into a new writable folder, separate from your own application. Open DatePicker.mcproj in McBasic™. Keep every declared source, layout, resource and migration file together.

To reconstruct it yourself, create a DesktopApp project and add the files declared below. In the complete project, follow these steps as a guided rebuild: replace each named source file once and Check after all its procedures are present.

Exact project configuration
DatePicker.mcproj
{
  "schemaVersion": 1,
  "projectId": "75f3d208-cf6f-4aa2-a1ad-3db0b9f2fb42",
  "name": "DatePickerSample",
  "kind": "DesktopApp",
  "language": {
    "dialect": "McBasic1",
    "requireExplicit": true,
    "compare": "Binary",
    "defaultArrayBase": 0
  },
  "application": {
    "bundleIdentifier": "com.mcbasic.samples.datepicker",
    "version": "0.1.0",
    "buildNumber": "1",
    "startupFormId": "form-main",
    "shutdownMode": "OnStartupFormClosed"
  },
  "forms": [
    {
      "id": "form-main",
      "typeName": "frmMain",
      "layout": "Forms/frmMain.form.json",
      "code": "Forms/frmMain.bas"
    }
  ],
  "modules": [],
  "classes": [],
  "tests": [],
  "references": [],
  "resources": [],
  "targets": [
    "osx-arm64"
  ],
  "capabilities": []
}

Step 2Build the Form and set its properties#

frmMain

Select the Form first and set its properties. Add containers before their children. These are initial Designer values, not statements to paste into a procedure.

Form propertyValue
Caption"DatePicker — McBasic"
Width560
Height300
MinWidth440
MinHeight240
TypeNameParent
DatePickerdtpDateForm
LabellblStatusForm
CommandButtoncmdClearForm
CommandButtoncmdCloseForm
dtpDate · exact Inspector values
PropertyValue
Left48
Top72
Width220
Height34
Value"2026-01-01"
MinimumDate"2023-01-01"
MaximumDate"2028-12-31"
Format"Custom"
CustomFormat"yyyy-MM-dd"
IsEmptyFalse
TabIndex0
Anchor edgesLeft, Top
lblStatus · exact Inspector values
PropertyValue
Left48
Top128
Width460
Height36
Caption"Date: 2026-01-01"
Anchor edgesLeft, Top
cmdClear · exact Inspector values
PropertyValue
Left48
Top192
Width140
Height36
Caption"Clear"
TabIndex1
Anchor edgesLeft, Top
cmdClose · exact Inspector values
PropertyValue
Left204
Top192
Width140
Height36
Caption"Close"
TabIndex2
Anchor edgesLeft, Top

Step 3Connect the events explicitly#

frmMain

ObjectEventProcedureParameters
dtpDateChangedtpDate_ChangeChange()
cmdClearClickcmdClear_ClickClick()
cmdCloseClickcmdClose_ClickClick()
FormLoadForm_Load()

Step 4Enter the complete behavior#

Open the named source file. Enter declarations first, then every procedure. Expand a procedure for its full body, or copy the complete file. Helpers are required: do not stop after entering the first Click handler.

Forms/frmMain.bas

Enter these declarations at file scope, before the procedures.

Forms/frmMain.bas · declarations
Option Explicit
Private Sub Form_Load()

Initialize state before enabling dependent actions. Keep the shared declarations and startup dependencies with this procedure.

Forms/frmMain.bas · Form_Load
Private Sub Form_Load()
    dtpDate.MinimumDate = CDate(45000)
    dtpDate.MaximumDate = CDate(47000)
    dtpDate.CustomFormat = "yyyy-MM-dd"
    dtpDate.Format = "Custom"
    dtpDate.ReadOnly = False
    dtpDate.IsEmpty = False
    dtpDate.Value = CDate(46000)
    lblStatus.Caption = "Date: " & dtpDate.Value
End Sub
Private Sub dtpDate_Change()

Read the current value or selection and update its dependent interface. The binding above determines which object calls this handler.

Forms/frmMain.bas · dtpDate_Change
Private Sub dtpDate_Change()
    If dtpDate.IsEmpty Then
        lblStatus.Caption = "No date selected."
    Else
        lblStatus.Caption = "Date changed: " & dtpDate.Value
    End If
End Sub
Private Sub cmdClear_Click()

Enter the complete action, including its input checks and calls to helper procedures.

Forms/frmMain.bas · cmdClear_Click
Private Sub cmdClear_Click()
    dtpDate.IsEmpty = True
    lblStatus.Caption = "No date selected."
End Sub
Private Sub cmdClose_Click()

Enter the complete action, including its input checks and calls to helper procedures.

Forms/frmMain.bas · cmdClose_Click
Private Sub cmdClose_Click()
    Unload Me
End Sub
Copy the complete Forms/frmMain.bas file

Replace the file once; do not append duplicate procedures.

Forms/frmMain.bas
Option Explicit

Private Sub Form_Load()
    dtpDate.MinimumDate = CDate(45000)
    dtpDate.MaximumDate = CDate(47000)
    dtpDate.CustomFormat = "yyyy-MM-dd"
    dtpDate.Format = "Custom"
    dtpDate.ReadOnly = False
    dtpDate.IsEmpty = False
    dtpDate.Value = CDate(46000)
    lblStatus.Caption = "Date: " & dtpDate.Value
End Sub

Private Sub dtpDate_Change()
    If dtpDate.IsEmpty Then
        lblStatus.Caption = "No date selected."
    Else
        lblStatus.Caption = "Date changed: " & dtpDate.Value
    End If
End Sub

Private Sub cmdClear_Click()
    dtpDate.IsEmpty = True
    lblStatus.Caption = "No date selected."
End Sub

Private Sub cmdClose_Click()
    Unload Me
End Sub

Step 5Keep resources and storage reproducible#

No external resource or migration files are declared. Any inline migration, seed data or local JSON is present in the code above. Runtime application data and private preferences are not included in the archive.

Step 6Check, run and test the result#

Save all files and run Check. Resolve diagnostics before Run. Developer CLI users can work from the extracted folder:

Developer CLI
mcbasic check DatePicker.mcproj
mcbasic run DatePicker.mcproj

Acceptance checklist

  • Choose a date and inspect the displayed result.
  • Use the clear button and confirm no stale date is shown as selected.
  • Choose a new date after clearing.

Step 7Make one change and repeat the tests#

Make the output explain the empty state explicitly before you add persistence.

Save a working Git checkpoint first. Change one behavior, Check again and repeat the acceptance checklist. Compare with the downloaded solution if a regression appears.

Source baseline 20f4bfed6b · Build manifest