McBasic™ 0.7.881 · Build 881 · 7 min read

Hands-on tutorial · Language

Use With without losing object identity

Reduce repeated qualifiers while understanding the captured receiver.

2 Form / control designs2 complete BASIC filesGuided sample project

Download complete project Complete event code

With captures its receiver when the block begins. Reassigning a variable inside a nested block does not retarget the already-captured receiver. The sample deliberately creates distinct Forms to make that rule observable; read the identity comparison before simplifying this code.

Step 1Prepare a safe practice project#

Extract the archive into a new writable folder, separate from your own application. Open WithBlocks.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

WithBlocks.mcproj

{
  "schemaVersion": 1,
  "projectId": "099e2901-076d-45d1-9a8b-960147278d86",
  "name": "WithBlocks",
  "kind": "DesktopApp",
  "language": {
    "dialect": "McBasic1",
    "requireExplicit": true,
    "compare": "Binary",
    "defaultArrayBase": 0
  },
  "application": {
    "bundleIdentifier": "com.mcbasic.samples.withblocks",
    "version": "0.1.0",
    "buildNumber": "111",
    "startupFormId": "form-main",
    "shutdownMode": "OnStartupFormClosed"
  },
  "forms": [
    {
      "id": "form-main",
      "typeName": "frmMain",
      "layout": "Forms/frmMain.form.json",
      "code": "Forms/frmMain.bas"
    },
    {
      "id": "form-details",
      "typeName": "frmDetails",
      "layout": "Forms/frmDetails.form.json",
      "code": "Forms/frmDetails.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 property	Value
`Caption`	`"With Blocks - McBasic"`
`Width`	`520`
`Height`	`280`
`MinWidth`	`500`
`MinHeight`	`210`

Type	Name	Parent
TextBox	`txtName`	Form
CommandButton	`cmdGreet`	Form
Label	`lblGreeting`	Form
CommandButton	`cmdDetails`	Form

txtName · exact Inspector values

Property	Value
`Left`	`24`
`Top`	`32`
`Width`	`310`
`Height`	`36`
`Text`	`""`
`TabIndex`	`0`
Anchor edges	Left, Top

cmdGreet · exact Inspector values

Property	Value
`Left`	`354`
`Top`	`32`
`Width`	`130`
`Height`	`36`
`Caption`	`"Greet"`
`TabIndex`	`1`
Anchor edges	Left, Top

lblGreeting · exact Inspector values

Property	Value
`Left`	`24`
`Top`	`98`
`Width`	`460`
`Height`	`50`
`Caption`	`"Enter your name and click Greet."`
Anchor edges	Left, Top

cmdDetails · exact Inspector values

Property	Value
`Left`	`24`
`Top`	`166`
`Width`	`180`
`Height`	`36`
`Caption`	`"Compare references"`
`TabIndex`	`2`
Anchor edges	Left, Top

frmDetails

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 property	Value
`Caption`	`"With reference details"`
`Width`	`420`
`Height`	`220`

Type	Name	Parent
Label	`lblName`	Form
CommandButton	`cmdClose`	Form

lblName · exact Inspector values

Property	Value
`Left`	`24`
`Top`	`32`
`Width`	`370`
`Height`	`44`
`Caption`	`"Details"`
Anchor edges	Left, Top

cmdClose · exact Inspector values

Property	Value
`Left`	`24`
`Top`	`100`
`Width`	`160`
`Height`	`36`
`Caption`	`"Close details"`
`TabIndex`	`0`
Anchor edges	Left, Top

Step 3Connect the events explicitly#

frmMain

Object	Event	Procedure	Parameters
`cmdGreet`	`Click`	`cmdGreet_Click`	`Click()`
`cmdDetails`	`Click`	`cmdDetails_Click`	`Click()`

frmDetails

Object	Event	Procedure	Parameters
`cmdClose`	`Click`	`cmdClose_Click`	`Click()`
Form	`Shown`	`Form_Shown`	`()`

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 cmdGreet_Click()

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

Forms/frmMain.bas · cmdGreet_Click

Private Sub cmdGreet_Click()
    With Me
        With .txtName
            .Text = Trim(.Text)
        End With
        If Len(txtName.Text) = 0 Then
            .lblGreeting.Caption = "Enter a name."
            Exit Sub
        End If
        With .lblGreeting
            .Caption = "Hello, " & txtName.Text & "!"
        End With
    End With
End Sub

Private Sub cmdDetails_Click()

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

Forms/frmMain.bas · cmdDetails_Click

Private Sub cmdDetails_Click()
    Dim original As frmDetails, current As frmDetails
    Set original = New frmDetails
    Set current = original
    With current
        .DisplayName = "first"
        With (current)
            Set current = New frmDetails
            .DisplayName = "captured"
        End With
        .DisplayName = txtName.Text
        .Show
    End With
    With lblGreeting
        .Caption = "Captured=" & original.DisplayName & "; distinct=" & Not (original Is current)
    End With
    Unload original
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 cmdGreet_Click()
    With Me
        With .txtName
            .Text = Trim(.Text)
        End With
        If Len(txtName.Text) = 0 Then
            .lblGreeting.Caption = "Enter a name."
            Exit Sub
        End If
        With .lblGreeting
            .Caption = "Hello, " & txtName.Text & "!"
        End With
    End With
End Sub

Private Sub cmdDetails_Click()
    Dim original As frmDetails, current As frmDetails
    Set original = New frmDetails
    Set current = original
    With current
        .DisplayName = "first"
        With (current)
            Set current = New frmDetails
            .DisplayName = "captured"
        End With
        .DisplayName = txtName.Text
        .Show
    End With
    With lblGreeting
        .Caption = "Captured=" & original.DisplayName & "; distinct=" & Not (original Is current)
    End With
    Unload original
End Sub

`Forms/frmDetails.bas`

Enter these declarations at file scope, before the procedures.

Forms/frmDetails.bas · declarations

Option Explicit

Public DisplayName As String

Private Sub Form_Shown()

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

Forms/frmDetails.bas · Form_Shown

Private Sub Form_Shown()
    With Me
        With .lblName
            .Caption = "Details for " & DisplayName
        End With
    End With
End Sub

Private Sub cmdClose_Click()

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

Forms/frmDetails.bas · cmdClose_Click

Private Sub cmdClose_Click()
    With Me
        .Unload
    End With
End Sub

Copy the complete Forms/frmDetails.bas file

Replace the file once; do not append duplicate procedures.

Forms/frmDetails.bas

Option Explicit

Public DisplayName As String

Private Sub Form_Shown()
    With Me
        With .lblName
            .Caption = "Details for " & DisplayName
        End With
    End With
End Sub

Private Sub cmdClose_Click()
    With Me
        .Unload
    End With
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 WithBlocks.mcproj
mcbasic run WithBlocks.mcproj

Acceptance checklist

Greet with padded input and verify trimming.
Open details and inspect the captured/distinct status.
Trace which instance receives each DisplayName assignment.

Step 7Make one change and repeat the tests#

Rewrite the greeting without With and confirm the same output for empty and nonempty input.

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

Use With without losing object identity

Step 1Prepare a safe practice project#

Step 2Build the Form and set its properties#

frmMain

frmDetails

Step 3Connect the events explicitly#

frmMain

frmDetails

Step 4Enter the complete behavior#

Forms/frmMain.bas

Forms/frmDetails.bas

Step 5Keep resources and storage reproducible#

Step 6Check, run and test the result#

Acceptance checklist

Step 7Make one change and repeat the tests#

Continue learning#

`Forms/frmMain.bas`

`Forms/frmDetails.bas`