Elixir - 调用/调用宏 - UndefinedFunctionError

Question

为什么Elixir 在使用文件中的语法UndefinedFunctionError调用宏时报告？我似乎只能调用宏,如果我有另一个调用宏的函数,我调用函数而不是宏.Module.macroName.exs

下面的代码演示了这个

defmodule Sample do
  defmacro doIt(expression) do
    quote do
      IO.puts unquote(expression)
    end
  end

  def doFunc(e), do: doIt(e)
end

Sample.doFunc "Hello World via Function" # Works fine
Sample.doIt "Hello World from Macro!" # Gives error

产量

Hello World via Function
** (UndefinedFunctionError) undefined function: Sample.doIt/1
    Sample.doIt("Hello World from Macro!")
    (elixir) lib/code.ex:307: Code.require_file/2

该药剂文档示例使用iex,而不是在调用宏.exs文件.即使是上面的代码,如果我们删除调用Sample.doIt 并加载它iex,然后调用Sample.doIt工作正常.

E:\elixir>iex hello.exs
Hello World via Function
Interactive Elixir (1.0.4) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> require Sample
nil
iex(2)> Sample.doIt "Hello"
Hello
:ok
iex(3)>

如果我尝试require Sample在上面的文件中,如下所示

defmodule Sample
  ... rest of stuff as shown above ...
end

require Sample

Sample.doFunc "Hello World via Function"
Sample.doIt "Hello World from Macro!"

我收到错误

** (CompileError) hello.exs:11: module Sample is not loaded but was defined. This happens because you are trying to use a module in the same context it is defined. Try defining the module outside the context that requires it.
    (stdlib) lists.erl:1352: :lists.mapfoldl/3
    (stdlib) lists.erl:1353: :lists.mapfoldl/3

Answer 1

像往常一样,在使用宏之前需要一个模块来向编译器表明编译模块的顺序:

defmodule Other do
  def run do
    require Sample

    Sample.doFunc "Hello World via Function"
    Sample.doIt "Hello World from Macro!"
  end
end

Other.run # => Hello World via Function
          #    Hello World from Macro!