[英]Javascript: array member variable not working as instance variable in prototypical inheritance
我試圖在我的代碼中使用javascript繼承。 以下是相同的jsfiddle。 http://jsfiddle.net/Fetsz/3/
var baseObject = Object.create(Object, {
// this works as an instance variable for derived objects
name: {
writable: true,
configurable: true,
enumerable: true,
value: null
},
// this should act as instance variable for derived objects
values: {
writable: true,
configurable: true,
enumerable: true,
value: []
},
displayAlert: {
value: function (){
alert("Alert from base object");
}
}
});
var derivedObj1 = Object.create(baseObject, {});
var derivedObj2 = Object.create(baseObject, {});
function displayValues (obj) {
alert("values for " + obj.name + "\n" + JSON.stringify(obj.values));
};
$(document).ready(function(){
derivedObj1.name = "Object 1";
derivedObj2.name = "Object 2";
derivedObj1.values.push("DO1 element");
derivedObj2.values.push("DO2 element");
derivedObj1.displayAlert();
// should display values added only for derivedObj1
displayValues(derivedObj1);
// should display values added only for derivedObj2
displayValues(derivedObj2);
});
我還檢查了以下問題,很好地解釋了為什么我的代碼不起作用。 Javascript繼承:Parent的數組變量保留值
我需要在每個派生類中都有一個數組成員變量,它將包含某些值。 我試圖通過在基類中添加數組來實現相同的目標。 正如上面提到的問題,為了實現相同的目的,我將不得不為每個派生類添加數組成員。 有沒有其他方法來實現這一點而不修改每個派生類?
創建它們時, derivedObj1.values
和derivedObj2.values
指向同一個數組對象。 如果你首先使用derivedObj1.values = [];
重新分配每一個derivedObj1.values = [];
,就像重新分配name
屬性一樣,您的代碼將按預期運行。
您可以創建一個將數組添加到實例的init
方法,而不是將values
屬性添加到原始baseObject:
var baseObject = Object.create(Object, {
// this works as an instance variable for derived objects
name: {
writable: true,
configurable: true,
enumerable: true,
value: null
},
// this should act as instance variable for derived objects
init: {
writable: true,
configurable: true,
enumerable: true,
value: function(){
this.values = [];
}
},
displayAlert: {
value: function (){
alert("Alert from base object");
}
}
});
var derivedObj1 = Object.create(baseObject, {});
derivedObj1.init();
var derivedObj2 = Object.create(baseObject, {});
derivedObj2.init();
如果您不希望所有實例共享變量,則您的變量不能在原型上。 您可以僅使用數組的屬性定義創建第二個對象,並將其作為第二個參數傳遞給Object.create
:
var arrDef = {
values: {
writable: true,
configurable: true,
enumerable: true,
value: []
}
}
var derivedObj1 = Object.create(baseObject, arrDef);
var derivedObj2 = Object.create(baseObject, arrDef);
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