Question

我想这样做：检查是否提供了callback，所以我按照以下步骤操作。我想知道的是：

我可以检查最后一个元素吗？
实际上在某些情况下可能会失败：如果最后一个元素是函数但它不是callbak。

这是代码

_deferred = Q.defer()
[before..., last] = args
if typeof last is 'function'
    args = before
    cb = last
else
  cb = (err, results) ->
      if err?
          _deferred.reject(err)
      else
          _deferred.resolve(results)
// ... other code

Answer 1

更短的版本是＆＃34; split＆＃34;函数参数列表中的参数：

fn = (args..., cb) ->
    _deferred = Q.defer()

    # if cb is a function, it gets assigned to callback
    # and we skip the following statements because not (true and true) == false
    if not (typeof cb is 'function' and callback = cb)
        # cb is not a function so it's just another arg
        args.push cb
        callback = (err, results) ->
            if err? then _deferred.reject(err) else _deferred.resolve(results)

    console.log args
    console.log callback.toSource() # Function.toSource() only works on Firefox
    # ... other code

fn 'arg1', 'arg2', 'arg3', () -> 'foo'

关于你的第二个问题，只有你知道什么是真实的＆＃34;回调是否。如果您无法按类型确定，则可以更改fn参数格式，例如，传递对象：

params =
    callback: () -> 'foo'
    args: [ 'arg1', 'arg2', 'arg3', () -> 'bar' ]

fn2 = ({ callback, args }) ->
    callback = callback or (err, results) ->
        if err? then _deferred.reject(err) else _deferred.resolve(results)

    console.log args
    console.log callback.toSource() # again, this only works in Firefox


fn2(params)

Answer 2

Build Phases > Embed Frameworks

更好的方法来检查coffeescript中的最后一个元素？

2 个答案: