33 lines
827 B
TypeScript
33 lines
827 B
TypeScript
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import AbstractDerivation from './AbstractDerivation'
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import type {IDerivation} from './IDerivation'
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// Exporting from a function because of the circular dependency with AbstractDerivation
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const makeMapDerivationClass = () =>
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class MapDerivation<T, V> extends AbstractDerivation<V> {
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constructor(
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private readonly _dep: IDerivation<T>,
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private readonly _fn: (t: T) => V,
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) {
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super()
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this._addDependency(_dep)
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}
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_recalculate() {
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return this._fn(this._dep.getValue())
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}
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_reactToDependencyBecomingStale() {}
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}
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let cls: ReturnType<typeof makeMapDerivationClass> | undefined = undefined
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export default function flatMap<V, R>(
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dep: IDerivation<V>,
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fn: (v: V) => R,
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): IDerivation<R> {
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if (!cls) {
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cls = makeMapDerivationClass()
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}
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return new cls(dep, fn)
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}
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