在自定义类上使用JSON.stringify [英] Using JSON.stringify on custom class

问题描述

我正在尝试将对象存储在redis中，redis是类的实例，因此具有功能，这是一个示例:

I'm trying to store an object in redis, which is an instance of a class, and thus has functions, here's an example:

function myClass(){
    this._attr = "foo";
    this.getAttr = function(){
        return this._attr;
    }
}

有没有一种方法可以将对象与函数一起存储在Redis中?我尝试了JSON.stringify()，但是仅保留了属性.如何存储函数定义并能够执行以下操作:

Is there a way to store this object in redis, along with the functions? I tried JSON.stringify() but only the properties are preserved. How can I store the function definitions and be able to perform something like the following:

var myObj = new myClass();
var stringObj = JSON.stringify(myObj);
// store in redis and retreive as stringObj again
var parsedObj = JSON.parse(stringObj);

console.log(myObj.getAttr()); //prints foo
console.log(parsedObj.getAttr()); // prints "Object has no method 'getAttr'"

调用parsedObj.getAttr()时如何获取foo?

提前谢谢！

编辑

建议修改MyClass.prototype并存储值，但是类似这样的事情(除setter/getter之外的功能)是

Got a suggestion to modify the MyClass.prototype and store the values, but what about something like this (functions other than setter/getter):

function myClass(){
    this._attr = "foo";
    this._accessCounts = 0;
    this.getAttr = function(){
        this._accessCounts++;
        return this._attr;
    }
    this.getCount = function(){
        return this._accessCounts;
    }
}

我正在尝试说明一个函数，该函数除了执行其他操作外，还可以在每次调用时计算计数或平均值.

I'm trying to illustrate a function that calculates something like a count or an average whenever it is called, apart from doing other stuff.

推荐答案

首先，您没有定义类.

这只是一个对象，其属性的值是一个函数(在创建新的 instance 时，将复制其在构造函​​数中定义的所有成员函数，这就是为什么说这不是一堂课.)

It's just an object, with a property whose value is a function (All its member functions defined in constructor will be copied when create a new instance, that's why I say it's not a class.)

使用JSON.stringify时将被剥夺.

考虑使用的是使用V8的node.js，最好的方法是定义一个真实的类，并使用__proto__播放一些魔术.无论您在类中使用了多少个属性(只要每个属性都使用原始数据类型)，该方法就可以正常工作.

Consider you are using node.js which is using V8, the best way is to define a real class, and play a little magic with __proto__. Which will work fine no matter how many property you used in your class (as long as every property is using primitive data types.)

这里是一个例子:

function MyClass(){
  this._attr = "foo";
}
MyClass.prototype = {
  getAttr: function(){
    return this._attr;
  }
};
var myClass = new MyClass();
var json = JSON.stringify(myClass);

var newMyClass = JSON.parse(json);
newMyClass.__proto__ = MyClass.prototype;

console.log(newMyClass instanceof MyClass, newMyClass.getAttr());

它将输出:

true "foo"

这篇关于在自定义类上使用JSON.stringify的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！