Elixir Ecto : Could someone give an example of Ecto. Multi.run/5

Question

docs状态

run(t, name, module, function, args) :: t when function: atom, args: [any]

Similar to run/3, but allows to pass module name, function and arguments. The function should return either {:ok, value} or {:error, value}, and will receive changes so far as the first argument (prepened to those passed in the call to the function).

但我不确定如何使用它。假设我想在 Ecto.Multi 中运行这个函数:

def some_fun(value, other_value) do
  case value do
    nil -> {:error, other_value}
    _ -> {:ok, other_value}
  end
end

那将如何运作？

Answer 1

我假设你想要 value成为“迄今为止的变化”和other_value是您在调用 Multi.run/5 时指定的值.在这种情况下，如果您的函数位于名为 Foo 的模块中:

defmodule Foo do
  def some_fun(value, other_value) do
    case value do
      nil -> {:error, other_value}
      _ -> {:ok, other_value}
    end
  end
end

那么你的 Multi.run/5电话将是:

Multi.run(multi, name, Foo, :some_fun, [other_value])

相当于下面的 Multi.run/3称呼:

Multi.run(multi, name, fn value -> Foo.some_fun(value, other_value) end)