Javascript：從指針修改對象

我正在製作一個帶有三個類的數字圖書館：Library，Shelf & Book。書架上有許多書籍的內容。書籍有兩種方法，enshelf和unshelf。當一本書被取消時，它應該設置刪除它自己的實例，然後將它的位置屬性設置爲null。我怎樣才能修改它所坐的架子？在構造函數中，如果我改變this.location，它只會給該屬性一個新值，而不是修改它指向的變量。我覺得這很簡單，我忽略了一些超級基礎。Javascript：從指針修改對象

var _ = require('lodash'); 

//books 
var oldMan = new Book("Old Man and the Sea", "Ernest Hemingway", 0684801221); 
var grapes = new Book("The Grapes of Wrath", "John Steinbeck", 0241952476); 
var diamondAge = new Book("The Diamond Age", "Neal Stephenson", 0324249248); 

//shelves 
var shelf0 = new Shelf(0); 
var shelf1 = new Shelf(1); 

//libraries 
var myLibrary = new Library([shelf0, shelf1], "123 Fake Street"); 

//these need to accept an unlimited amount of each 
function Library(shelves, address) { 
    this.shelves = shelves; //shelves is an array 
    this.address = address; 
    this.getAllBooks = function() { 
     console.log("Here are all the books in the library: "); 
     for (var i = 0; i < this.shelves.length; i++) { 
      console.log("Shelf number " + i + ": "); 
      for (var j = 0; j < this.shelves[i].contents.length; j++) { 
       console.log(this.shelves[i].contents[j].name); 
      } 
     } 
    } 
} 

function Shelf(id) { 
    this.id = id; 
    this.contents = []; 
} 

function Book(name, author, isbn) { 
    this.name = name; 
    this.author = author; 
    this.isbn = isbn; 
    this.location = null; 
    this.enshelf = function(newLocation) { 
     this.location = newLocation; 
     newLocation.contents.push(this); 
    } 
    this.unshelf = function() { 
     _.without(this.location, this.name); //this doesn't work 
     this.location = null; 
    } 
} 


console.log("Welcome to Digital Library 0.1!"); 

oldMan.enshelf(shelf1); 
myLibrary.getAllBooks(); 
oldMan.unshelf(); 
myLibrary.getAllBooks();

來源

2014-09-20 ajHurliman

使用[] .splice（）進行修改，像_.without功能的解決方案（）進行復印。 – dandavis 2014-09-20 23:52:41

小問題，你unshelf方法，容易補救：

this.unshelf = function() { 
    this.location.contents = 
     _.without(this.location.contents, this); 
    this.location = null; 
}

考慮，但是，shelf和unshelf應該是Shelf方法，而不是Book。另外，如果你必須有這種方法，圍繞着它有一個後衛，就像這樣：

this.unshelf = function() { 
    if (this.location) { 
     this.location.contents = 
      _.without(this.location.contents, this); 
     this.location = null; 
    } 
}

來源

2014-09-20 23:10:51

太棒了，謝謝:)） – ajHurliman 2014-09-21 01:37:14

幾個小問題：

without作品的陣列和返回刪除元素的數組的副本 - 原文未觸及。因此，您需要通過location.contents而不是僅僅location和將其重新分配給location.contents。

此外，您還將整本書添加到書架，然後嘗試通過名稱將其刪除，因此它不匹配並被刪除。所以只是通過this到without：

this.unshelf = function() { 
    if (this.location) { 
     this.location.contents = _.without(this.location.contents, this); 
     this.location = null; 
    } 
}

來源

2014-09-20 23:15:17 Rhumborl

Javascript：從指針修改對象

回答

相關問題