javascript設計モード第四章

引き継ぐ
 
親類

/* Class Person. */

function Person(name) {
  this.name = name;
}

Person.prototype.getName = function() {
  return this.name;
}

var reader = new Person('John Smith');
reader.getName();

 1、プロトタイプチェーン

/* Class Author. */

function Author(name, books) {
  Person.call(this, name); // Call the superclass' constructor in the scope of this.
  this.books = books; // Add an attribute to Author.
}

Author.prototype = new Person(); // Set up the prototype chain.
Author.prototype.constructor = Author; // Set the constructor attribute to Author.
Author.prototype.getBooks = function() { // Add a method to Author.
  return this.books;
};

var author = [];
author[0] = new Author('Dustin Diaz', ['JavaScript Design Patterns']);
author[1] = new Author('Ross Harmes', ['JavaScript Design Patterns']);

author[1].getName();
author[1].getBooks();

 2、exted関数
派の子供の種類の全体の過程を1つのextedという関数の中で包装します.

/* Extend function. */

function extend(subClass, superClass) {
  var F = function() {};
  F.prototype = superClass.prototype;
  subClass.prototype = new F();
  subClass.prototype.constructor = subClass;
}

/* Class Author. */

function Author(name, books) {
  Person.call(this, name);
  this.books = books;
}
extend(Author, Person);

Author.prototype.getBooks = function() {
  return this.books;
};

 改善後のコード:

/* Extend function, improved. */

function extend(subClass, superClass) {
  var F = function() {};
  F.prototype = superClass.prototype;
  subClass.prototype = new F();
  subClass.prototype.constructor = subClass;

  subClass.superclass = superClass.prototype;
  if(superClass.prototype.constructor == Object.prototype.constructor) {
    superClass.prototype.constructor = superClass;
  }
}


/* Class Author. */

function Author(name, books) {
  Author.superclass.constructor.call(this, name);
  this.books = books;
}
extend(Author, Person);

Author.prototype.getBooks = function() {
  return this.books;
};

Author.prototype.getName = function() {
  var name = Author.superclass.getName.call(this);
  return name + ', Author of ' + this.getBooks().join(', ');
};

 3、元を混ぜる

/* Mixin class. */

var Mixin = function() {};
Mixin.prototype = {
  serialize: function() {
    var output = [];
    for(key in this) {
      output.push(key + ': ' + this[key]);
    }
    return output.join(', ');
  }
};

augment(Author, Mixin);

var author = new Author('Ross Harmes', ['JavaScript Design Patterns']);
var serializedString = author.serialize();

/* Augment function. */

function augment(receivingClass, givingClass) {
  for(methodName in givingClass.prototype) { 
    if(!receivingClass.prototype[methodName]) {
      receivingClass.prototype[methodName] = givingClass.prototype[methodName];
    }
  }
}

/* Augment function, improved. */

function augment(receivingClass, givingClass) {
  if(arguments[2]) { // Only give certain methods.
    for(var i = 2, len = arguments.length; i < len; i++) {
      receivingClass.prototype[arguments[i]] = givingClass.prototype[arguments[i]];
    }
  } 
  else { // Give all methods.
    for(methodName in givingClass.prototype) { 
      if(!receivingClass.prototype[methodName]) {
        receivingClass.prototype[methodName] = givingClass.prototype[methodName];
      }
    }
  }
}

 
引き継ぐ メモリを消費する
原型 setとgetは統一するように注意してください.
元を混ぜる 拡張クラス