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node_modules/matrix-widget-api/src/util/SimpleObservable.ts

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+/*
+ * Copyright 2020 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export type ObservableFunction<T> = (val: T) => void;
+
+export class SimpleObservable<T> {
+    private listeners: ObservableFunction<T>[] = [];
+
+    public constructor(initialFn?: ObservableFunction<T>) {
+        if (initialFn) this.listeners.push(initialFn);
+    }
+
+    public onUpdate(fn: ObservableFunction<T>): void {
+        this.listeners.push(fn);
+    }
+
+    public update(val: T): void {
+        for (const listener of this.listeners) {
+            listener(val);
+        }
+    }
+
+    public close(): void {
+        this.listeners = []; // reset
+    }
+}