Umbrella Projects

实际上有时工程项目会变得很大. Mix 构建工具可以让我们将代码划分成多个程序, 使得项目变大的时候更易于管理.
介绍
创建一个 umbrella project 就像我们创建 Mix project 时一样, 只是多传入了 --umbrella 标志. 下面的例子中我们将创建一个机器学习的命令行工具. 你问为什么是一个机器学习工具? 为什么不呢? 它们将由一些学习算法和通用函数组成.
$ mix new machine_learning_toolkit --umbrella
​
* creating .gitignore
* creating README.md
* creating mix.exs
* creating apps
* creating config
* creating config/config.exs
​
Your umbrella project was created successfully.
Inside your project, you will find an apps/ directory
where you can create and host many apps:
​
    cd machine_learning_toolkit
    cd apps
    mix new my_app
​
Commands like "mix compile" and "mix test" when executed
in the umbrella project root will automatically run
for each application in the apps/ directory.
正如你在 shell 命令中看到的, Mix 为我们创建了一个项目的框架, 并有两个目录:
apps/ - 我们子项目所在的地方
config/ - 我们 umbrella 项目配置文件所在的地方
子项目
让我们切换到项目的 machine_learning_toolkit/apps 目录并用 Mix 创建三个普通的项目:
$ mix new utilities
​
* creating README.md
* creating .gitignore
* creating mix.exs
* creating config
* creating config/config.exs
* creating lib
* creating lib/utilities.ex
* creating test
* creating test/test_helper.exs
* creating test/utilities_test.exs
​
Your Mix project was created successfully.
You can use "mix" to compile it, test it, and more:
​
    cd utilities
    mix test
​
Run "mix help" for more commands.
​
​
$ mix new datasets
​
* creating README.md
* creating .gitignore
* creating mix.exs
* creating config
* creating config/config.exs
* creating lib
* creating lib/datasets.ex
* creating test
* creating test/test_helper.exs
* creating test/datasets_test.exs
​
Your Mix project was created successfully.
You can use "mix" to compile it, test it, and more:
​
    cd datasets
    mix test
​
Run "mix help" for more commands.
​
$ mix new svm
​
* creating README.md
* creating .gitignore
* creating mix.exs
* creating config
* creating config/config.exs
* creating lib
* creating lib/svm.ex
* creating test
* creating test/test_helper.exs
* creating test/svm_test.exs
​
Your Mix project was created successfully.
You can use "mix" to compile it, test it, and more:
​
    cd svm
    mix test
​
Run "mix help" for more commands.
现在我们项目中的文件结构应该像这样:
$ tree
.
├── README.md
├── apps
│   ├── datasets
│   │   ├── README.md
│   │   ├── config
│   │   │   └── config.exs
│   │   ├── lib
│   │   │   └── datasets.ex
│   │   ├── mix.exs
│   │   └── test
│   │       ├── datasets_test.exs
│   │       └── test_helper.exs
│   ├── svm
│   │   ├── README.md
│   │   ├── config
│   │   │   └── config.exs
│   │   ├── lib
│   │   │   └── svm.ex
│   │   ├── mix.exs
│   │   └── test
│   │       ├── svm_test.exs
│   │       └── test_helper.exs
│   └── utilities
│       ├── README.md
│       ├── config
│       │   └── config.exs
│       ├── lib
│       │   └── utilities.ex
│       ├── mix.exs
│       └── test
│           ├── test_helper.exs
│           └── utilities_test.exs
├── config
│   └── config.exs
└── mix.exs
当切回 umbrella 项目的根目录时, 可以发现我们可以调用所有常见的命令, 比如: compile(编译). 所有的子项目也是普通的 application，你可以切到他们的目录和通常项目一样做 Mix 可以做的事.
$ mix compile
​
==> svm
Compiled lib/svm.ex
Generated svm app
​
==> datasets
Compiled lib/datasets.ex
Generated datasets app
​
==> utilities
Compiled lib/utilities.ex
Generated utilities app
​
Consolidated List.Chars
Consolidated Collectable
Consolidated String.Chars
Consolidated Enumerable
Consolidated IEx.Info
Consolidated Inspect
IEx
你也许认为和 umbrella 项目在 IEx 中交互会有些区别. 不管你信不信, 你猜错了! 当我们切到顶层目录并用 iex -S mix 启动 IEx, 我们可以正常的和所有项目进行交互. 让我们改变一下 apps/datasets/lib/datasets.ex 的内容来举个例子:
defmodule Datasets do
  def hello do
    IO.puts("Hello, I'm the datasets")
  end
end
$ iex -S mix
Erlang/OTP {{ site.erlang.OTP }} [erts-{{ site.erlang.erts }}] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]
​
==> datasets
Compiled lib/datasets.ex
Consolidated List.Chars
Consolidated Collectable
Consolidated String.Chars
Consolidated Enumerable
Consolidated IEx.Info
Consolidated Inspect
Interactive Elixir ({{ site.elixir.version }}) - press Ctrl+C to exit (type h() ENTER for help)
​
iex> Datasets.hello
:world
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Last updated 4 months ago