can-define

Exports the define method that defines observable properties and their behavior on a prototype object.

`define(prototype, propDefinitions)`

Define observable properties, type conversion, and getter/setter logic on prototype objects.

var define = require("can-define");

var Greeting = function(message){
    this.message = message;
};

define(Greeting.prototype,{
    message: {type: "string"}
});

Parameters

prototype {Object}:
The prototype object of a constructor function or class. The prototype object will have getter/setters defined on it that carry out the defined behavior. The prototype will also contain all of can-event's methods.
propDefinitions {Object<String,PropDefinition>}:
An object of properties and their definitions.

Use

can-define provides a way to create custom types with observable properties. Where can-define/map/map and can-define/list/list provide more functionality, they also make more assumptions on the type constructor. can-define can be used to create completely customized types.

The following creates a Person constructor function:

var define = require("can-define");

var Person = function(first, last){
  this.first = first;
  this.last = last;
};
define(Person.prototype,{
  first: { type: "string" },
  last: { type: "string" },
  fullName: {
    get: function(){
      return this.first+" "+this.last;
    }
  }
});

This can be used to create Person instances with observable properties:

var person = new Person("Justin", "Meyer");
person.first    //-> "Justin"
person.last     //-> "Meyer"
person.fullName //-> "Justin Meyer"

person.on("fullName", function(ev, newVal, oldVal){
    newVal //-> "Ramiya Meyer"
    oldVal //-> "Justin Meyer"
});

person.first = "Ramiya"

The observable properties call Observation.add so they can be observed by can-compute.