从构造函数实例化的类范围对象

Question

使用下面的 someAPI，它需要我想在构造函数中动态分配的凭据。然后我想在整个课程中使用 someAPI。 IE。在下面的示例中，someMethodUsingSomeAPI 是我想从 B 实例中的其他方法调用的辅助方法。Coffee-/JavaScript 可以做到这一点吗？ （我可以让它工作的唯一方法是将 someMethodUsingSomeAPI 放在构造函数中。）

SomeAPI = Npm.require 'someAPI'

class B extends A
  constructor: (options = {}) ->
    unless @ instanceof B
      return new B(options)

    @config = JSON.parse(Assets.getText('config/' + options.username + '.json'))

    @someAPI = new SomeAPI
      consumer_key: @config.credentials.consumer.key
      consumer_secret: @config.credentials.consumer.secret
      access_token: @config.credentials.access.token
      access_token_secret: @config.credentials.access.secret

  someMethodUsingSomeAPI = Async.wrap((id, callback) ->
    return @someAPI.get 'whatever/show', { 'id': id }, callback
  )

  console.log someMethodUsingSomeAPI '123' # Error: Cannot call method 'get' of undefined

根据 saimeunt 的建议进行了更新

...

someMethodUsingSomeAPI = (id) ->
  wrappedGet = Async.wrap(@someAPI, 'get')
  wrappedGet 'whatever/show', { id: id }

console.log someMethodUsingSomeAPI '123' # ReferenceError: someMethodUsingSomeAPI is not defined

&

b = B('username')
b.someMethodUsingSomeAPI '123' # Works!

将someMethodUsingSomeAPI: 更改为someMethodUsingSomeAPI =

console.log someMethodUsingSomeAPI '123' # Error: unsupported argument list

&

b = B('username')
b.someMethodUsingSomeAPI '123' # TypeError: Object #<B> has no method 'someMethodUsingSomeAPI'

（这是 Meteor 0.9.3.1）

更新试图澄清

Here's a simplified version of the above, without any of the API stuff.

someMethod = works, someMethod: doesn't work

我很高兴classInstance.someMethod 在使用 : 时可以正常工作，但我真的很想让它在实际实例中工作。

Answer 1

当然，您可以将someAPI 附加到您的类对象上。在 coffeescript 中，@ 用于代替 this（就像在 Javscript 中一样）。

SomeAPI = require 'someAPI'

class A extends B
  constructor: (options = {}) ->
    unless @ instanceof A
      return new A(options)

    @config = JSON.parse('config/' + options.username + '.json')

    @someAPI = new SomeAPI
      consumer_key: @config.credentials.consumer.key
      consumer_secret: @config.credentials.consumer.secret
      access_token: @config.credentials.access.token
      access_token_secret: @config.credentials.access.secret

  someMethodUsingSomeAPI:  (id, callback) ->
    return @someAPI.get 'whatever/show', { 'id': id }, callback

您可以查看 this SO question，它解释了 Javascript this 及其范围。一旦你明白了，看看coffeescript's classes是如何工作的，你应该对@的使用有一定的了解。

Answer 2

我想这就是你想要的：

someMethodUsingSomeAPI:function(id){
  var wrappedGet=Async.wrap(@someAPI,"get");
  return wrappedGet("whatever/show",{
    id:id
  });
}

Answer 3

根据您在此处提供的简化示例，该版本应符合您的要求：

class SomeClass
  # Store the last created instance at the class level
  lastInstance: null

  constructor: (options = {}) ->
    @someLastName = options.someLastName 
    # In constructor, the created instance is now the lastInstance
    SomeClass.lastInstance = this

# The helper method is not created in the class scope
someMethod = (someFirstName) ->
  "Hello " + someFirstName + " " + SomeClass.lastInstance.someLastName

someClass = new SomeClass({ someLastName: 'Borgnine' })

alert someMethod 'Ernest'

还有here's a link to try it in a browser。

基本上，由于您希望您的辅助方法访问该类的实例，因此您需要提供对该实例的引用，该实例可以在某个时候引用。在这里，我使用一个类变量来存储最后创建的实例，并且助手在调用时访问最后一个实例。这意味着当创建许多实例时，它将执行如下：

someClass = new SomeClass({ someLastName: 'Borgnine' })

alert someMethod 'Ernest' # Hello Ernest Borgnine

someClass = new SomeClass({ someLastName: 'Doe' })

alert someMethod 'Boris' # Hello Boris Doe