auto-object

Create an object or a class that may accessed by any property name just like Proxy.

eg.

const myObject = autoObject.createObject(function(name) {
    if(name.startsWith("say")) {
        return function() {
            return name.substr(3);
        }
    }
 
    return name;
});
 
myObject.foo;       ///< "foo"
myObject.sayFoo();  ///< "Foo"
myObject.sayBar();  ///< "Bar"

Installation

$ npm install --save auto-object

API

Require auto-object at first:

const autoObject = require("auto-object");

createClass

Create an auto-object class and get its constructor function:

autoObject.createClass([className])

• className: the class name, default to AutoClass. (optional)
• return: the special constructor function

Your own constructor function should attached on the prototype chain named $$constructor. And the access function should attached on the prototype chain named $$access. Both of $$constructor and $$access are optional.

What's $$constructor

We usually create a class constructor function like this:

function MyClass(val) {
    this.$val = val;
}

But createClass exactly returns a constructor function which you can't redefine. So we make $$constructor as your own constructor function.

eg.

const MyClass = autoObject.createClass("MyClass");
 
MyClass.prototype.$$constructor = function(val) {
    this.$$val = val;
};
 
const ret = new MyClass(233); ///< MyClass { $$val: 233 }

What's $$access

$$access is the access function to deal with property accessing. This function owns a single parameter which means the property name. You should return a result for the accessing.

eg.

const MyClass = autoObject.createClass("MyClass");
 
MyClass.prototype.$$constructor = function(val) {
    this.$$val = val;
};
 
MyClass.prototype.$$access = function(property) {
    const self = this;
    if(property.match(/^plus\d+$/)) {
        return function() {
            self.$$val += parseInt(property.substr(4));
            return $$val;
        };
    } else if(property.match(/^minus\d+$/)) {
        return function() {
            self.$$val -= parseInt(property.substr(5));
            return $$val;
        };
    }
 
    return "You're hacked";
};
 
const ret = new MyClass(233);   ///< MyClass { $$val: 233 }
ret.plus5();                    ///< 238
ret.plus2();                    ///< 240
ret.minus10();                  ///< 230
ret.foo;                        ///< "You're hacked"

Inherits

The result of createClass almost like the normal constructor function, it may inherit from some other class by using util.inherits too.

eg.

const MyClass = autoObject.createClass("MyClass");
 
MyClass.prototype.$$constructor = function() {
    EventEmitter.call(this);
};
 
util.inherits(MyClass, EventEmitter);
 
MyClass.prototype.$$access = function(name) {
    const self = this;
    return function(val) {
        self.emit(name, val);
    };
}
 
const ret = new MyClass();
ret.on("test", function(val) {
    console.log(val);
});
ret.test("Hello world");        // emit("test", "Hello world")

createObject

Create and get an auto-object:

autoObject.createObject([access]);

• access: the access function. (optional)
• return: the special auto-object

If you want to change access function lately, you just assign the function to the $$access property of the returned object.

What's $$access

$$access is the access function to deal with property accessing. This function owns a single parameter which means the property name. You should return a result for the accessing.

eg.

const obj = autoObject.createObject(function(name) {
    return `You're ${name}`;
});
 
obj.foo;        ///< "You're foo"
obj.bar;        ///< "You're bar"

You can change $$access at any time you want to do this.

eg.

const obj = autoObject.createObject();
 
obj.foo;                        ///< undefined
obj.$$access = function(name) {
    return `You're ${name}`;
};
obj.foo;                        ///< "You're foo"
obj.bar;                        ///< "You're bar"

Reserved Properties and Overwrite Rule

This is important!

Here's a reserved properties list that won't go through the access function:

[
  "constructor",
  "hasOwnProperty",
  "isPrototypeOf",
  "propertyIsEnumerable",
  "toLocaleString",
  "toString",
  "valueOf",
  "__defineGetter__",
  "__defineSetter__",
  "__lookupGetter__",
  "__lookupSetter__",
  "__proto__",
  "inspect",
  "$$constructor",
  "$$access"
]

And if you define a property manually in your auto-object, that certain property won't go through the access function too.

eg.

const obj = autoObject.createObject(function() {
    return "You're hacked";
});
 
obj.foo;                ///< "You're hacked"
obj.foo = "I'm free";
obj.foo;                ///< "I'm free"
delete obj.foo;
obj.foo;                ///< "You're hacked"

Hacking util.inherits*

If you're using Node.js v4.x or you're considering to backward compatible v4.x in your program, you should not use util.inherits to inherit your Auto-Object class.

As a substitute, you should use autoObject.inherits instead. This function is same as util.inherits when you're using v6.x or higher. But if you're using v4.x, it's a hacking.

The code is like this under v4.x:

for(const key in superCtor.prototype) {
    ctor.prototype[key] = superCtor.prototype[key];
}

The behavior is not 100% same as util.inherits. So in fact I don't recommend you use this package under v4.x.

Contribution

You're welcome to fork and make pull requests!

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