| 1 | {"version":3,"file":"ref.js","sources":["../src/directives/ref.ts"],"sourcesContent":["/**\n * @license\n * Copyright 2020 Google LLC\n * SPDX-License-Identifier: BSD-3-Clause\n */\nimport {nothing, ElementPart} from '../lit-html.js';\nimport {directive, AsyncDirective} from '../async-directive.js';\n\n/**\n * Creates a new Ref object, which is container for a reference to an element.\n */\nexport const createRef = <T = Element>() => new Ref<T>();\n\n/**\n * An object that holds a ref value.\n */\nclass Ref<T = Element> {\n /**\n * The current Element value of the ref, or else `undefined` if the ref is no\n * longer rendered.\n */\n readonly value?: T;\n}\n\nexport type {Ref};\n\ninterface RefInternal {\n value: Element | undefined;\n}\n\n// When callbacks are used for refs, this map tracks the last value the callback\n// was called with, for ensuring a directive doesn't clear the ref if the ref\n// has already been rendered to a new spot\nconst lastElementForCallback: WeakMap<Function, Element | undefined> =\n new WeakMap();\n\nexport type RefOrCallback = Ref | ((el: Element | undefined) => void);\n\nclass RefDirective extends AsyncDirective {\n private _element?: Element;\n private _ref?: RefOrCallback;\n private _context: unknown;\n\n render(_ref: RefOrCallback) {\n return nothing;\n }\n\n override update(part: ElementPart, [ref]: Parameters<this['render']>) {\n const refChanged = ref !== this._ref;\n if (refChanged && this._ref !== undefined) {\n // The ref passed to the directive has changed;\n // unset the previous ref's value\n this._updateRefValue(undefined);\n }\n if (refChanged || this._lastElementForRef !== this._element) {\n // We either got a new ref or this is the first render;\n // store the ref/element & update the ref value\n this._ref = ref;\n this._context = part.options?.host;\n this._updateRefValue((this._element = part.element));\n }\n return nothing;\n }\n\n private _updateRefValue(element: Element | undefined) {\n if (typeof this._ref === 'function') {\n // If the current ref was called with a previous value, call with\n // `undefined`; We do this to ensure callbacks are called in a consistent\n // way regardless of whether a ref might be moving up in the tree (in\n // which case it would otherwise be called with the new value before the\n // previous one unsets it) and down in the tree (where it would be unset\n // before being set)\n if (lastElementForCallback.get(this._ref) !== undefined) {\n this._ref.call(this._context, undefined);\n }\n lastElementForCallback.set(this._ref, element);\n // Call the ref with the new element value\n if (element !== undefined) {\n this._ref.call(this._context, element);\n }\n } else {\n (this._ref as RefInternal)!.value = element;\n }\n }\n\n private get _lastElementForRef() {\n return typeof this._ref === 'function'\n ? lastElementForCallback.get(this._ref)\n : this._ref?.value;\n }\n\n override disconnected() {\n // Only clear the box if our element is still the one in it (i.e. another\n // directive instance hasn't rendered its element to it before us); that\n // only happens in the event of the directive being cleared (not via manual\n // disconnection)\n if (this._lastElementForRef === this._element) {\n this._updateRefValue(undefined);\n }\n }\n\n override reconnected() {\n // If we were manually disconnected, we can safely put our element back in\n // the box, since no rendering could have occurred to change its state\n this._updateRefValue(this._element);\n }\n}\n\n/**\n * Sets the value of a Ref object or calls a ref callback with the element it's\n * bound to.\n *\n * A Ref object acts as a container for a reference to an element. A ref\n * callback is a function that takes an element as its only argument.\n *\n * The ref directive sets the value of the Ref object or calls the ref callback\n * during rendering, if the referenced element changed.\n *\n * Note: If a ref callback is rendered to a different element position or is\n * removed in a subsequent render, it will first be called with `undefined`,\n * followed by another call with the new element it was rendered to (if any).\n *\n * ```js\n * // Using Ref object\n * const inputRef = createRef();\n * render(html`<input ${ref(inputRef)}>`, container);\n * inputRef.value.focus();\n *\n * // Using callback\n * const callback = (inputElement) => inputElement.focus();\n * render(html`<input ${ref(callback)}>`, container);\n * ```\n */\nexport const ref = directive(RefDirective);\n\n/**\n * The type of the class that powers this directive. 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