@openui5/sap.ui.core
Version:
OpenUI5 Core Library sap.ui.core
65 lines (58 loc) • 2.06 kB
JavaScript
/*!
* OpenUI5
* (c) Copyright 2009-2021 SAP SE or an SAP affiliate company.
* Licensed under the Apache License, Version 2.0 - see LICENSE.txt.
*/
/*
* IMPORTANT: This is a private module, its API must not be used and is subject to change.
* Code other than the OpenUI5 libraries must not introduce dependencies to this module.
*/
sap.ui.define([], function() {
"use strict";
/**
* Creates a property stub which allows to retrieve the corresponding property value lazily.
*
* <b>Note:</b> Within the callback, the property value shows as undefined and
* should not be set other than via assignment (no <code>Object.defineProperty</code>).
* The function callback should return the actual property's value like that:
* <pre>
* sap.ui.require(["sap/base/util/defineLazyProperty"], function(defineLazyProperty){
* var oTarget = {};
* defineLazyProperty(oTarget, "sProp", function() {
* return 7;
* });
* console.log(oTarget["sProp"]); // should be 7
* });
* </pre>
*
* @function
* @since 1.58
* @alias module:sap/base/util/defineLazyProperty
* @param {object} oTarget Target object of the property stub
* @param {string} sProperty Name of the stubbed property
* @param {function} fnCallback Function callback which returns the property value
* @param {function} [sMarker] Marker to allow identification of the according property descriptor
* like <code>Object.getOwnPropertyDescriptor(oTarget, sProperty).get[sMarker]</code>
* @private
* @ui5-restricted sap.ui.core
*/
var lazyProperty = function(oTarget, sProperty, fnCallback, sMarker) {
var oPropertyDescriptor = {
configurable: true,
get: function() {
delete oTarget[sProperty];
oTarget[sProperty] = fnCallback();
return oTarget[sProperty];
},
set: function(vValue) {
delete oTarget[sProperty];
oTarget[sProperty] = vValue;
}
};
if (sMarker) {
oPropertyDescriptor.get[sMarker] = true;
}
Object.defineProperty(oTarget, sProperty, oPropertyDescriptor);
};
return lazyProperty;
});