| 1 | import { getAtom, observe } from "mobx";
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| 2 | /**
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| 3 | * MobX normally suspends any computed value that is not in use by any reaction,
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| 4 | * and lazily re-evaluates the expression if needed outside a reaction while not in use.
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| 5 | * `keepAlive` marks a computed value as always in use, meaning that it will always fresh, but never disposed automatically.
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| 6 | *
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| 7 | * @example
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| 8 | * const obj = observable({
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| 9 | * number: 3,
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| 10 | * doubler: function() { return this.number * 2 }
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| 11 | * })
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| 12 | * const stop = keepAlive(obj, "doubler")
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| 13 | *
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| 14 | * @param {Object} target an object that has a computed property, created by `@computed` or `extendObservable`
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| 15 | * @param {string} property the name of the property to keep alive
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| 16 | * @returns {IDisposer} stops this keep alive so that the computed value goes back to normal behavior
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| 17 | */
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| 18 | /**
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| 19 | * @example
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| 20 | * const number = observable(3)
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| 21 | * const doubler = computed(() => number.get() * 2)
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| 22 | * const stop = keepAlive(doubler)
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| 23 | * // doubler will now stay in sync reactively even when there are no further observers
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| 24 | * stop()
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| 25 | * // normal behavior, doubler results will be recomputed if not observed but needed, but lazily
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| 26 | *
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| 27 | * @param {IComputedValue<any>} computedValue created using the `computed` function
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| 28 | * @returns {IDisposer} stops this keep alive so that the computed value goes back to normal behavior
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| 29 | */
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| 30 | export function keepAlive(_1, _2) {
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| 31 | var computed = getAtom(_1, _2);
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| 32 | if (!computed)
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| 33 | throw new Error("No computed provided, please provide an object created with `computed(() => expr)` or an object + property name");
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| 34 | return observe(computed, function () { });
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| 35 | }
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