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+# method
+
+[![Build Status](https://secure.travis-ci.org/Gozala/method.png)](http://travis-ci.org/Gozala/method)
+
+Library provides an API for defining polymorphic methods that dispatch on the
+first argument type. This provides a powerful way for decouple abstraction
+interface definition from an actual implementation per type, without risks
+of interference with other libraries.
+
+### Motivation
+
+  - Provide a high-performance, dynamic polymorphism construct as an
+    alternative to existing object methods that does not provides any
+    mechanics for guarding against name conflicts.
+  - Allow independent extension of types, and implementations of methods
+    on types, by different parties.
+
+## Install
+
+    npm install method
+
+## Use
+
+```js
+var method = require("method")
+
+// Define `isWatchable` method that can be implemented for any type.
+var isWatchable = method("isWatchable")
+
+// If you call it on any object it will
+// throw as nothing implements that method yet.
+//isWatchable({}) // => Exception: method is not implemented
+
+// If you define private method on `Object.prototype`
+// all objects will inherit it.
+Object.prototype[isWatchable] = function() {
+  return false;
+}
+
+isWatchable({}) // => false
+
+
+// Although `isWatchable` property above will be enumerable and there for
+// may damage some assumbtions made by other libraries. There for it"s
+// recomended to use built-in helpers methods that will define extension
+// without breaking assumbtions made by other libraries:
+
+isWatchable.define(Object, function() { return false })
+
+
+// There are primitive types in JS that won"t inherit methods from Object:
+isWatchable(null) // => Exception: method is not implemented
+
+// One could either implement methods for such types:
+isWatchable.define(null, function() { return false })
+isWatchable.define(undefined, function() { return false })
+
+// Or simply define default implementation:
+isWatchable.define(function() { return false })
+
+// Alternatively default implementation may be provided at creation:
+isWatchable = method(function() { return false })
+
+// Method dispatches on an first argument type. That allows us to create
+// new types with an alternative implementations:
+function Watchable() {}
+isWatchable.define(Watchable, function() { return true })
+
+// This will make all `Watchable` instances watchable!
+isWatchable(new Watchable()) // => true
+
+// Arbitrary objects can also be extended to implement given method. For example
+// any object can simply made watchable:
+function watchable(object) {
+  return isWatchable.implement(objct, function() { return true })
+}
+
+isWatchable(watchable({})) // => true
+
+// Full protocols can be defined with such methods:
+var observers = "observers@" + module.filename
+var watchers = method("watchers")
+var watch = method("watch")
+var unwatch = method("unwatch")
+
+watchers.define(Watchable, function(target) {
+  return target[observers] || (target[observers] = [])
+})
+
+watch.define(Watchable, function(target, watcher) {
+  var observers = watchers(target)
+  if (observers.indexOf(watcher) < 0) observers.push(watcher)
+  return target
+})
+unwatch.define(Watchable, function(target, watcher) {
+  var observers = watchers(target)
+  var index = observers.indexOf(watcher)
+  if (observers.indexOf(watcher) >= 0) observers.unshift(watcher)
+  return target
+})
+
+// Define type Port that inherits form Watchable
+
+function Port() {}
+Port.prototype = Object.create(Watchable.prototype)
+
+var emit = method("emit")
+emit.define(Port, function(port, message) {
+  watchers(port).slice().forEach(function(watcher) {
+    watcher(message)
+  })
+})
+
+var p = new Port()
+watch(p, console.log)
+emit(p, "hello world") // => info: "hello world"
+```