@angular/core
Version:
Angular - the core framework
51 lines • 5.31 kB
JavaScript
/**
* @license
* Copyright Google Inc. All Rights Reserved.
*
* Use of this source code is governed by an MIT-style license that can be
* found in the LICENSE file at https://angular.io/license
*/
import { getClosureSafeProperty } from './property';
import { stringify } from './stringify';
var __forward_ref__ = getClosureSafeProperty({ __forward_ref__: getClosureSafeProperty });
/**
* Allows to refer to references which are not yet defined.
*
* For instance, `forwardRef` is used when the `token` which we need to refer to for the purposes of
* DI is declared, but not yet defined. It is also used when the `token` which we use when creating
* a query is not yet defined.
*
* @usageNotes
* ### Example
* {@example core/di/ts/forward_ref/forward_ref_spec.ts region='forward_ref'}
* @publicApi
*/
export function forwardRef(forwardRefFn) {
forwardRefFn.__forward_ref__ = forwardRef;
forwardRefFn.toString = function () { return stringify(this()); };
return forwardRefFn;
}
/**
* Lazily retrieves the reference value from a forwardRef.
*
* Acts as the identity function when given a non-forward-ref value.
*
* @usageNotes
* ### Example
*
* {@example core/di/ts/forward_ref/forward_ref_spec.ts region='resolve_forward_ref'}
*
* @see `forwardRef`
* @publicApi
*/
export function resolveForwardRef(type) {
var fn = type;
if (typeof fn === 'function' && fn.hasOwnProperty(__forward_ref__) &&
fn.__forward_ref__ === forwardRef) {
return fn();
}
else {
return type;
}
}
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