lazy.ts

/*!
 * Copyright (c) Microsoft Corporation and contributors. All rights reserved.
 * Licensed under the MIT License.
 */

/**
 * Helper class for lazy initialized values. Ensures the value is only generated once, and remain immutable.
 *
 * @deprecated Moved to the `@fluidframework/core-utils` package.
 * @internal
 */
export class Lazy<T> {
	private _value: T | undefined;
	private _evaluated: boolean = false;
	/**
	 * Instantiates an instance of Lazy<T>.
	 * @param valueGenerator - The function that will generate the value when value is accessed the first time.
	 */
	constructor(private readonly valueGenerator: () => T) {}

	/**
	 * Return true if the value as been generated, otherwise false.
	 */
	public get evaluated(): boolean {
		return this._evaluated;
	}

	/**
	 * Get the value. If this is the first call the value will be generated.
	 */
	public get value(): T {
		if (!this._evaluated) {
			this._evaluated = true;
			this._value = this.valueGenerator();
		}
		// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
		return this._value!;
	}
}