coffeescript - 从字符串中的类名实例化 CoffeeScript 类

Question

当字符串中只有类的名称时，如何在 CoffeeScript 中实例化类？

class Dog
  bark:->
    "Woof"

className = "Dog"
dog = new className  # <--- I would like to create an instance here using the string

Answer 1

稍有远见，您就可以轻松做到这一点，并保护自己免受使用 eval .在要按名称实例化的类的某处保留一个列表:

class Dog
  bark:->
    "Woof"

# Or window.named_classes if you need to access
# `named_classes` globally (or just in another
# CoffeeScript file).
named_classes = { Dog: Dog }

然后使用您的查找表而不是 eval :

name = 'Dog'
dog  = new named_classes[name]

当你说 class Dog ，你最终得到一个名为 Dog 的局部变量:

var Dog;
Dog = (function() { /* ... */ })();

并且无法获取本地 JavaScript 变量，除非您将其存储在可以通过名称访问的地方。另请注意 eval如果您定义 Dog 将不起作用在一个 CoffeeScript 文件中，并希望访问另一个文件，CoffeeScript wraps each file in self-executing anonymous function to limit variable scope :

all CoffeeScript output is wrapped in an anonymous function: (function(){ ... })(); This safety wrapper, combined with the automatic generation of the var keyword, make it exceedingly difficult to pollute the global namespace by accident.

If you'd like to create top-level variables for other scripts to use, attach them as properties on window, or on the exports object in CommonJS.