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2.8 KiB
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44 lines
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2.8 KiB
HTML
<!doctype html>
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<head>
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<meta charset="utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<title>query — Ludic</title>
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<meta name="description" content="Match every model instance carrying all the listed properties.">
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<link rel="stylesheet" href="base.css">
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<link rel="stylesheet" href="docs.css">
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</head>
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<body>
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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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<main class="wrap item">
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<div class="crumbs"><a href="api.html">API Reference</a> <span>›</span> <a href="api.html#ecs">Entities & the ECS</a> <span>›</span> <span class="here">query</span></div>
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<div class="item-head">
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<span class="kind-badge kind-keyword">keyword</span>
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<h1 id="top">query</h1>
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</div>
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<code class="sig">query [PropA, PropB, {Tag}]</code>
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<div class="desc"><p>A <code>query</code> selects every live model instance that carries <b>all</b> the listed properties, and is the core way handlers reach data. Use it in a <code>for (…) in query [...]</code> loop, where you write one loop variable per bound property in declaration order; each pass binds those properties for one matching instance and <code>self()</code> gives that instance. A <code>{Model}</code> term in tag position filters by model kind without binding a variable, so <code>query [Position, {Player}]</code> walks only players. Add a <code>where</code> clause to filter on field values (<code>where health.current > 0</code>). Matching is lazy and re-checked per instance as the loop reaches each id, not snapshotted, so spawns and despawns during the loop follow well-defined rules.</p></div>
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<div class="examples"><h2>Example</h2><pre data-lang="ludic">program Collisions {
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property Position { column: int = 0, row: int = 0 }
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property Health { current: int = 100, maximum: int = 100 }
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model Enemy { Position, Health }
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handler Boot phase Start {
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spawn Grunt { Position { column: 5, row: 5 }; Health { current: 10 } }
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}
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handler DrawWorld phase Render {
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Screen.clear(Color.MidnightBlue)
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for (position, health) in query [Position, Health, {Enemy}] where health.current > 0 {
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Screen.fill_rectangle(x: position.column * 16, y: position.row * 16, width: 16, height: 16, color: Color.Crimson)
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}
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Screen.show()
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}
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}</pre></div>
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<a class="back" href="api.html">← All symbols</a>
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</main>
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<script src="ludic-highlight.js"></script>
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<script>Ludic.highlightAll(); Ludic.installCards(); Ludic.flashTarget();</script>
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</body></html> |