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48 lines
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2.7 KiB
HTML
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<title>@OnDetach — Ludic</title>
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<meta name="description" content="Run a handler when a property is structurally detached from 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">@OnDetach</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">@OnDetach</h1>
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</div>
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<code class="sig">@OnDetach(Property) handler Name { … }</code>
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<div class="desc"><p><code>@OnDetach(Property)</code> is the teardown counterpart to <code>@OnAttach</code>: it fires when the named property is structurally removed from a live instance with <code>detach P on e</code>. The hook runs <b>before</b> the property's presence flag clears, so its body can still read the outgoing field values one last time — useful for releasing whatever the property was tracking or logging its final state. It is distinct from <code>@OnDisable</code>, which pauses a property while keeping its data; detach actually destroys the property's presence on the instance. Add <code>@Public</code> to also emit a <code>prop_<Property>_detach</code> event.</p></div>
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<div class="examples"><h2>Example</h2><pre data-lang="ludic">program DetachHook {
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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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@OnDetach(Shield) handler DropShield { # fires as Shield is removed
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print(Shield.amount + 20) # 25 — reads the outgoing amount
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}
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handler Seed phase Start {
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spawn Unit { Tag { value: 1 } }
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for (unit) in query [Unit] { attach Shield on self() { amount: 5 } }
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}
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handler RemoveShield phase Render {
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for (shield) in query [Shield] {
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detach Shield on self() # triggers @OnDetach
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}
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quit()
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}
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}</pre></div>
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