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41 lines
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2.8 KiB
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<title>world_field_id — Ludic</title>
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<meta name="description" content="Resolve a field name within a property to its numeric index.">
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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#ecs">Entities & the ECS</a> <span>›</span> <span class="here">world_field_id</span></div>
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<div class="item-head">
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<span class="kind-badge kind-builtin">function</span>
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<h1 id="top">world_field_id</h1>
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</div>
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<code class="sig">world_field_id(property, name) -> int</code>
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<div class="desc"><p><code>world_field_id</code> resolves a field name <b>within</b> a given property to its numeric index, which is what <code>world_get</code> and <code>world_set</code> use to pick which field to read or write. You pass a property id (from <code>world_prop_id</code>) and the field's name, and get back its index (negative if the property has no such field). Together the trio <code>world_prop_id</code> → <code>world_field_id</code> → <code>world_get</code>/<code>world_set</code> lets a mod or tool touch any field on any instance entirely by name, without the property being known at compile time.</p></div>
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<div class="params"><h2>Parameters</h2><div class="param" id="param-property"><code class="pname">property</code><span class="pdesc">the property id, from <code>world_prop_id</code></span></div><div class="param" id="param-name"><code class="pname">name</code><span class="pdesc">the field's name within that property, e.g. <code>"column"</code></span></div></div>
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<div class="examples"><h2>Example</h2><pre data-lang="ludic">program ResolveField {
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property Position { column: int = 0, row: int = 0 }
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model Player { Position }
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handler Boot phase Start {
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spawn Hero { Position { column: 3, row: 3 } }
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}
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handler Inspect phase Update {
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let position_property = world_prop_id("Position")
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let column_field = world_field_id(position_property, "column")
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Screen.status(string(column_field))
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}
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}</pre></div>
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