Define component parameter contracts — Build the smallest useful slice

PART I

Warm-up

Reconnect with a useful idea before starting define component parameter contracts. 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

Choose a default that preserves caller meaning

A component parameter contract states representation, meaning, allowed range, defaults and update behavior. A correct-looking configuration can violate any one of these. Keep the public contract independent from the native hosts private implementation; proposed WS object notation does not validate inputs by itself.

A Notice component accepts optional severity in info, warning, error. Omitted severity defaults to info; explicit empty text is invalid. Message is required and nonempty.

Worked reasoning: Message Saved with omitted severity becomes info. Message Failed with severity error stays error. Empty severity does not count as omission and must not silently default.

Failed alternative: Using a general falsy check collapses omitted and empty values even though the contract assigns them different meanings.

Worked reasoning and supplied artifact

Input{message:Saved} ->severity info
Input{message:Failed,severity:error} ->error
Input{message:Saved,severity:""} ->reject
Default applies only when field absent

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: Accessible service console. Build a small, understandable change around define component parameter contracts.

Specify an optional alignment default start with allowed start, center, end. Distinguish omission, empty and explicit end.

What to produce

A default-resolution table and explicit invalid-value policy.

• 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.button;
import wuix.layout;
domain Login {
    const screen = {
        layout: { type: "column", padding: [24, 32], gap: 16 },
        components: [{ type: "text", value: "Welcome back" }]
    };
    fnc show() -> void {
        wuix.mount("main", screen);
    }
}

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.

• Choose a default that preserves caller meaning
• Specify an optional alignment default start with allowed start, center, end. Distinguish omission, empty and explicit end.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Represent absence distinctly before applying defaults.

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