forked from EVOgeek/Vmeda.Online
41 lines
1.3 KiB
TypeScript
41 lines
1.3 KiB
TypeScript
// (C) Copyright 2015 Moodle Pty Ltd.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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* Lazy map.
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*
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* Lazy maps are empty by default, but entries are generated lazily when accessed.
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*/
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export type LazyMap<T> = Record<string, T>;
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/**
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* Create a map that will initialize entries lazily with the given constructor.
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*
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* @param lazyConstructor Constructor to use the first time an entry is accessed.
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* @returns Lazy map.
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*/
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export function lazyMap<T>(lazyConstructor: (key: string) => T): LazyMap<T> {
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const instances = {};
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return new Proxy(instances, {
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get(target, property, receiver) {
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if (!(property in instances)) {
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target[property] = lazyConstructor(property.toString());
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}
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return Reflect.get(target, property, receiver);
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},
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});
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}
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