Use validated handles instead of raw pointers — Boundary detective

PART I

Warm-up

Reconnect with a useful idea before starting use validated handles instead of raw pointers. In one or two sentences, describe the input, output or host boundary from the previous exercise that this lesson builds on. If you are arriving directly, skim the worked example first; there is no locked prerequisite.

A rough note is enough. You can revise it after the example.

PART II

Instruction & guided example

Check a deleted resource

An automation extension should request narrowly authorized host operations on validated resources. A token is an opaque reference with identity and lifetime, not a native address. Validate the operation at the host boundary even when the caller supplies a familiar-looking identifier.

Exercise host offers image resize on approved asset A for mod M. Handle a9 maps to A, generation 2, owner M, read/resize only. Asset B belongs to another mod. The source does not define token encoding or resize API signatures; these fixtures are plain request/decision records.

Supplied case: a9 still appears in an imported draft, but A was legitimately deleted before submission.

Worked reasoning: A valid-looking stored token can no longer resolve a live resource. Refuse unavailable and preserve the caller’s draft rather than creating a replacement silently. The result is distinct from permission denied.

Contrast and diagnosis: Guessing a new asset at the same slot breaks identity and may cross owners.

Worked reasoning and supplied artifact

// Disposable exercise fixture / host-contract notes; not executable API syntax.
// Supplied input: a9 still appears in an imported draft, but A was legitimately deleted before submission.
// Worked prediction: A valid-looking stored token can no longer resolve a live resource. Refuse unavailable and preserve the caller’s draft rather than creating a replacement silently. The result is distinct from permission denied.
// Rejected alternative: Guessing a new asset at the same slot breaks identity and may cross owners.

Illustrative example from the proposed WillowScript design. The language and WUIX/WMATH/WDB/WAUDIO/WTMP services are not implemented in the supplied source. This site has no interpreter, VM or native host and does not execute or certify the snippet.

Try the guided change

Reconstruct the supplied worked case first: list its inputs, intermediate decisions and final artifact. Compare each row with the explanation and identify exactly where the rejected alternative fails. Then use the changed inputs in Part IV for independent work.

• Write the supplied inputs and initial state before following the example.
• Reconstruct each intermediate calculation or host decision, then compare with the worked artifact.
• Explain why the contrasting alternative fails before attempting the changed inputs in Part IV.

PART III

Take a breather

Step back after the guided example. Look away from the screen, stretch, or reread your prediction. This is an optional learning pause, not a timer or an assessment gate.

When you return, try to name the lesson’s key idea without copying its wording. If that feels difficult, return to Part II and trace one line rather than restarting the entire lesson.

PART IV

Independent practice

Project context: Restricted automation extension. Build a small, understandable change around use validated handles instead of raw pointers.

Write decision categories for deleted, stale generation and denied operation handles.

What to produce

Write decision categories for deleted, stale generation and denied operation handles. Include input → intermediate decision/state → predicted outcome, with any required host rule stated explicitly.

• State the intended behavior in a sentence before editing.
• Use only source-backed syntax and the host services whose contract you have been given.
• Record a normal case and a boundary or unavailable-resource case.
• Label hand predictions separately from anything actually measured in a supplied toolchain.

Syntax colors are a reading aid, not a compiler. The line you are editing stays uncolored until you move to a different line; capitalization is never changed. Drafts stay on this browser and code is not executed.

import wuix.widget;
const button = widget.Button({
    text: "Continue",
    events: {
        click: fnc() -> void {
            navigator.open("dashboard");
        }
    }
});

PART V

Self-check

Use this check to notice what to revisit. It does not award a private course grade, block another page or claim to verify compiled code. Every answer has a learning explanation.

You may keep exploring even if you are unsure. Use the hint, compare the trace, and revise your explanation.

PART VI

Recap & small task

Bring the idea back to the mod feature you are building. A useful recap connects the mechanism to a decision you can make in your own code.

• Check a deleted resource
• Explain the decision for the supplied case, then independently work the changed fixture.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

In one or two sentences, name the decisive rule in “Check a deleted resource” and predict the outcome of one changed input from your independent fixture. State which host behavior still needs real verification.

This marks your personal practice record only. It is not a certification or an official workspace assessment.