在Elixir中定义一个常量模块 [英] Define a constant module in elixir

问题描述

我想创建一些可变的边界模块.理想情况下，结果看起来像任何其他模块一样，但是可以在编译时或在配置文件中设置行为.我想我正在寻找类似erlang的东西

说我有一个SystemClock模块和一个DummyClock元组模块.理想情况下，时钟"模块应该是配置文件中上面选择的两个模块中的一个或另一个.

在config/test.ex

define(Clock, {DummyClock, 12345678})

以后

Clock.now
# => 12345678

在config/prod.ex

中

define(Clock, SystemClock)

以后

Clock.now
# => 32145687

解决方案

我认为最简单的方法是使用configs和Application.get_env/2.

在config/test.exs

中

config :my_application, clock: DummyClock

在config/dev.exs和config/prod.exs

中

config :my_application, clock: RealClock

使用时钟的代码中

defp clock, do: Application.get_env(:my_application, :clock)

def my_function(arg1, arg2) do
  now = clock.now
  # ...
end

I would like to create some changeable boundary module. Ideally the result would look like any other module but the behaviour could be set at compile time or in the configuration files. I think I am looking for something like define in erlang

Say I have a SystemClock module and a DummyClock tuple module. Ideally the Clock module would be one or other of the two modules above chosen in the config file.

In config/test.ex

define(Clock, {DummyClock, 12345678})

Later

Clock.now
# => 12345678

In config/prod.ex

define(Clock, SystemClock)

Later

Clock.now
# => 32145687

解决方案

I think the easiest way to do this is with configs and Application.get_env/2.

in config/test.exs

config :my_application, clock: DummyClock

in config/dev.exs and config/prod.exs

config :my_application, clock: RealClock

in the code that uses the clock

defp clock, do: Application.get_env(:my_application, :clock)

def my_function(arg1, arg2) do
  now = clock.now
  # ...
end

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