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45 lines
No EOL
2.7 KiB
HTML
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<title>@OnAttach — Ludic</title>
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<meta name="description" content="Run a handler when a property is structurally attached to a live instance.">
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<header class="nav"><div class="wrap nav-in"><a class="brand" href="index.html"><span class="logo">L</span> Ludic</a><button class="nav-toggle" aria-label="Toggle menu" aria-expanded="false">☰</button><nav class="nav-links"><a href="index.html">Home</a><a href="api.html">API Reference</a><a class="nav-cta" href="https://git.workshopsoft.io/workshopsoft/ludic">Source ↗</a></nav></div></header>
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<div class="crumbs"><a href="api.html">API Reference</a> <span>›</span> <a href="api.html#annotations">Annotations</a> <span>›</span> <span class="here">@OnAttach</span></div>
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<div class="item-head">
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<span class="kind-badge kind-annotation">annotation</span>
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<h1 id="top">@OnAttach</h1>
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</div>
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<code class="sig">@OnAttach(Property) handler Name { … }</code>
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<div class="desc"><p><code>@OnAttach(Property)</code> fires when the named property is <b>structurally added</b> to a live model instance with <code>attach P on e</code> — the property's fields are seeded first, then the hook runs in the context of that instance so it can read and adjust them. This is the structural birth of a property, the counterpart to <code>@OnDetach</code>; it differs from <code>@OnEnable</code>, which only un-pauses a property that already exists. Use it to react when a capability appears on an instance at runtime — a shield goes up, a status effect lands. The property name is a checked reference. Add <code>@Public</code> to also emit a <code>prop_<Property>_attach</code> event.</p></div>
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<div class="examples"><h2>Example</h2><pre data-lang="ludic">program AttachHook {
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property Tag { value: int = 0 }
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property Shield { amount: int = 0 }
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model Unit { Tag }
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@OnAttach(Shield) handler RaiseShield { # fires when Shield is attached
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print(Shield.amount + 10) # 15 — reads the seeded amount
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}
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handler Seed phase Start { spawn Unit { Tag { value: 1 } } }
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handler AddShield phase Render {
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for (unit) in query [Unit] {
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attach Shield on self() { amount: 5 } # triggers @OnAttach
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}
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quit()
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}
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}</pre></div>
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