Model ordered lists, nested settings, and typed event configuration — Flash-check repair

PART I

Warm-up

Reconnect with a useful idea before starting model ordered lists, nested settings, and typed event configuration. 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

Repair an unrelated handler result contract

Typed event configuration must connect a declared callback contract to the actual delivery shape. Registration stores a response; delivery supplies inputs later. Shared fnc vocabulary does not make Event, navigator or an arbitrary event field a builtin. Treat every such name as an explicit exercise-host dependency.

Host selection callback expects fnc(event: Event)->void and ignores no alternate result channel. A draft returns an integer fee while failing to perform the required selection update. Event contains itemId6.

Worked reasoning: The callback result contract and the application effect are separate obligations. A correct response matches void and requests the documented selection update for6; computing fee6 is not a substitute. Unknown update signatures must remain host requirements.

Failed alternative: Changing only the annotation to i32 conflicts with the registered callback contract rather than making the host consume a new value.

Worked reasoning and supplied artifact

Required:Event(itemId6) ->void response +selection request6
Draft:Event(itemId6) ->integer fee,selection unchanged
Repair:agree on void signature;route itemId through supplied selection contract
No fabricated update API

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: Reusable configuration workspace. Build a small, understandable change around model ordered lists, nested settings, and typed event configuration.

Review a void Confirm callback that returns count3 instead of requesting confirmation. Identify signature and behavior defects separately.

What to produce

A callable-contract checklist plus a corrected effect-flow description.

• 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.

• Repair an unrelated handler result contract
• Review a void Confirm callback that returns count3 instead of requesting confirmation. Identify signature and behavior defects separately.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Check parameter types, result type and observable responsibility as separate rows.

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