使用 Node.js require 和 CoffeeScript 中的类解决循环依赖

We can improve on the above by moving the setup back into the concern of each individual submodule, and only removing the dependency management into the higher-level file. The dependencies will be acquired by the higher-level module (with no cycles), and then passed around as necessary:

# <a.coffee>
module.exports = ({B})-> ->
    # Each module, in addition to being wrapped in a closure-producing
    # function to allow us to close over the dependencies, is further
    # wrapped in a function that allows us to defer *construction*.
    B = B()

    class A extends require './c'
        b: new B

        someMethod: ->
            super

# <b.coffee>
module.exports = ({A})-> ->
    # Each module, in addition to being wrapped in a closure-producing
    # function to allow us to close over the dependencies, is further
    # wrapped in a function that allows us to defer *construction*.
    A = A()

    class B extends require './c'
        a: new A

        someMethod: ->
            super

# <my_library.coffee>
A = require './a'
B = require './b'

# First we close each library over its dependencies,
A = A(B)
B = B(A)

# Now we construct a copy of each (which each will then construct its own
# copy of its counterpart)
module.exports = A: A(), B: B()

# Consumers now get a constructed, final, 'normal' copy of each class.

太可怕了，因为:好吧，除了在这个特定场景中它绝对丑陋(！！?！)，你只是把解决依赖问题的问题推到了堆栈上给消费者.在这种情况下，那个消费者仍然是你自己，这很好......但是现在，当你想通过 require 公开 A alone 时会发生什么('my_library/a')?现在您必须向消费者说明他们必须使用 X、Y 和 Z 依赖项来参数化您的子模块……等等.进入兔子洞.

# <a.coffee>
module.exports =
class A extends require './c'

    @finish = ->
        require './b'
        @::b = new B

    someMethod: ->
        super

# <b.coffee>
module.exports =
class B extends require './c'

    @finish = ->
        require './a'
        @::a = new A

    someMethod: ->
        super

# <my_library.coffee>
A = require './a'
B = require './b'

module.exports = A: A.finish(), B: B.finish()