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2.5 KiB
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46 lines
No EOL
2.5 KiB
HTML
<!doctype html>
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<html lang="en">
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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>emit — Ludic</title>
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<meta name="description" content="Fire an event, running every listener; as an expression it yields the veto flag.">
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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#events">Events</a> <span>›</span> <span class="here">emit</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">emit</h1>
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</div>
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<code class="sig">emit Name(field: value)</code>
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<div class="desc"><p><code>emit Name(field: value, …)</code> fires an event: it runs every <code>@On(Name)</code> listener in declaration order, passing the named payload fields (any you omit take the event's declared defaults). It desugars to a direct call into the event's generated function, so firing an event is as cheap as calling a function. For a <code>cancellable</code> event, <code>emit</code> can be used as an <b>expression</b> that yields the cancelled flag — <code>0</code> if no listener vetoed, <code>1</code> if one did — which is the "check the decision before acting" shape: apply the effect only when the emit returns <code>0</code>.</p></div>
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<div class="examples"><h2>Example</h2><pre data-lang="ludic">program EmitExample {
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event cancellable BeforeSpend { amount: int = 0 }
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var coins: int = 50
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@On(BeforeSpend) handler RejectOverdraft { if amount > coins { cancel } }
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handler TrySpend phase Update {
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if Input.key() == 'b' {
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if emit BeforeSpend(amount: 20) == 0 { coins = coins - 20 }
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}
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}
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handler DrawWorld phase Render {
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Screen.clear(Color.MidnightBlue)
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Screen.draw_number(x: 4, y: 4, value: coins, color: Color.Gold, scale: 1)
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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> |