工欲善其事，必先利其器之—MAC下搭建scala的开发环境

前置环境

• 安装JDK(scala编译成java字节码，最终跑在jvm),需要java1.8以上的版本
• 安装Atom或IDEA

安装scala与sbt

使用homebrew安装scala sdk和可以构建scala应用的工具

brew install scala
brew install [e-mail]1

各工具的版本

• Scala : 2.12.6
• Sbt : 1.1.6
• IDEA : 2018.1.4
• Atom : 1.23.2

tips: 由于scala与sbt是使用brew安装的，可以用brew info命令查看它们的版本，示例如下

[e-mail]-MacBook-Pro hello-world-template$ brew info scala
scala: stable 2.12.6, devel 2.13.0-M3

命令行的Scala开发环境

1.cd到一个空的目录，运行如下命令创建一个模板工程

# 该命令会从github上下载一个模板工程（所有要用网络呀！）
luogw@luogw-MacBook-Pro hello-world-template$ sbt new scala/hello-world.g8
[info] Set current project to hello-world-template (in build file:/Users/luogw/temp/hello-world-template/)
[info] Set current project to hello-world-template (in build file:/Users/luogw/temp/hello-world-template/)

A template to demonstrate a minimal Scala application

name [Hello World template]:

# 直接回车，使用默认工程名即可
# 回车后多一个 hello-world-template

2.cd到hello-world-template目录，并运行sbt命令，进入sbt的交互模式

[e-mail] hello-world-template$ cd hello-world-template/
[e-mail] hello-world-template$ sbt
[info] Loading project definition from /Users/luogw/temp/hello-world-template/hello-world-template/project
[info] Updating ProjectRef(uri("file:/Users/luogw/temp/hello-world-template/hello-world-template/project/"), "hello-world-template-build")...
[info] Done updating.
[info] Loading settings from build.sbt ...
[info] Set current project to hello-world (in build file:/Users/luogw/temp/hello-world-template/hello-world-template/)
[info] sbt server started at local:///Users/luogw/.sbt/1.0/server/3bab035d199a92d0d5cc/sock
sbt:hello-world>

3.运行应用,在步骤2的基础上执行 ~run命令

sbt:hello-world> ~run
[info] Updating ...
[info] Done updating.
[info] Compiling 1 Scala source to /Users/luogw/temp/hello-world-template/hello-world-template/target/scala-2.12/classes ...
[info] Done compiling.
[info] Packaging /Users/luogw/temp/hello-world-template/hello-world-template/target/scala-2.12/hello-world_2.12-1.0.jar ...
[info] Done packaging.
[info] Running Main
Hello, World!
[success] Total time: 1 s, completed 2018-6-28 14:55:42
1. Waiting for source changes... (press enter to interrupt)

注：输出结果后，sbt交互界面挂起，一直监听项目代码文件的更改，这意味着你可以用喜欢的编辑器打开项目的某个文件编辑（如src/main/scala/Main.scala），编辑后保存文件，sbt交互终端将重新编译项目并运行,示例如下

Hello, World!
[success] Total time: 1 s, completed 2018-6-28 14:55:42
1. Waiting for source changes... (press enter to interrupt)
[info] Compiling 1 Scala source to /Users/luogw/temp/hello-world-template/hello-world-template/target/scala-2.12/classes ...
[info] Done compiling.
[info] Packaging /Users/luogw/temp/hello-world-template/hello-world-template/target/scala-2.12/hello-world_2.12-1.0.jar ...
[info] Done packaging.
[info] Running Main
Hello, World!, go go go
[success] Total time: 1 s, completed 2018-6-28 15:01:16
2. Waiting for source changes... (press enter to interrupt)

Atom下的Scala开发环境

安装插件: ensime（该插件能使scala工程被atom打开发，编辑源文件时有代码补全，高亮等的支持），并在其settings中更新配置
* ensime server version为 2.0.0-SNAPSHOT
* sbt的路径 /usr/local/bin/sbt (使用which命令可以找到sbt的位置)

[e-mail]-MacBook-Pro hello-world-template$ which sbt
/usr/local/bin/sbt

安装ensime-sbt的插件

在~/.sbt/1.0/plugins目录下新建文件plugins.sbt，并在文件中添加如下内容

addSbtPlugin("org.ensime" % "sbt-ensime" % "2.5.1")

创建工程

同命令行的scala开发环境步骤1

配置工程

在stb下运行 ensimeConfig,以便在当前工程下生成 .ensime 配置文件

[e-mail] hello-world-template$ sbt
[info] Loading settings from plugins.sbt ...
[info] Loading global plugins from /Users/luogw/.sbt/1.0/plugins
[info] Loading project definition from /Users/luogw/temp/hello-world-template/project
[info] Updating ProjectRef(uri("file:/Users/luogw/temp/hello-world-template/project/"), "hello-world-template-build")...
[info] Done updating.
[info] Loading settings from build.sbt ...
[info] Set current project to hello-world (in build file:/Users/luogw/temp/hello-world-template/)
[info] sbt server started at local:///Users/luogw/.sbt/1.0/server/d256dd7eefdec7178cf8/sock
sbt:hello-world> ensimeConfig
[info] ENSIME update.
[info] Updating ...
[info] Done updating.
[info] downloading https://repo1.maven.org/maven2/org/typelevel/cats-core_2.12/1.1.0/cats-core_2.12-1.1.0-javadoc.jar ...
[info] downloading https://repo1.maven.org/maven2/org/typelevel/machinist_2.12/0.6.2/machinist_2.12-0.6.2-javadoc.jar ...
[info] downloading https://repo1.maven.org/maven2/org/typelevel/cats-macros_2.12/1.1.0/cats-macros_2.12-1.1.0-javadoc.jar ...
[info] downloading https://repo1.maven.org/maven2/org/typelevel/cats-kernel_2.12/1.1.0/cats-kernel_2.12-1.1.0-javadoc.jar ...
[info]  [SUCCESSFUL ] org.typelevel#machinist_2.12;0.6.2!machinist_2.12.jar(doc) (3958ms)
[info] downloading https://repo1.maven.org/maven2/org/typelevel/machinist_2.12/0.6.2/machinist_2.12-0.6.2-sources.jar ...
[info]  [SUCCESSFUL ] org.typelevel#machinist_2.12;0.6.2!machinist_2.12.jar(src) (1052ms)
[info]  [SUCCESSFUL ] org.typelevel#cats-core_2.12;1.1.0!cats-core_2.12.jar(doc) (5747ms)
[info]  [SUCCESSFUL ] org.typelevel#cats-kernel_2.12;1.1.0!cats-kernel_2.12.jar(doc) (5813ms)
[info] downloading https://repo1.maven.org/maven2/org/typelevel/cats-core_2.12/1.1.0/cats-core_2.12-1.1.0-sources.jar ...
[info] downloading https://repo1.maven.org/maven2/org/typelevel/cats-kernel_2.12/1.1.0/cats-kernel_2.12-1.1.0-sources.jar ...
[info]  [SUCCESSFUL ] org.typelevel#cats-macros_2.12;1.1.0!cats-macros_2.12.jar(doc) (6355ms)
[info] downloading https://repo1.maven.org/maven2/org/typelevel/cats-macros_2.12/1.1.0/cats-macros_2.12-1.1.0-sources.jar ...
[info]  [SUCCESSFUL ] org.typelevel#cats-core_2.12;1.1.0!cats-core_2.12.jar(src) (1070ms)
[info]  [SUCCESSFUL ] org.typelevel#cats-kernel_2.12;1.1.0!cats-kernel_2.12.jar(src) (1037ms)
[info]  [SUCCESSFUL ] org.typelevel#cats-macros_2.12;1.1.0!cats-macros_2.12.jar(src) (1042ms)
[info] ENSIME processing hello-world-template (hello-world)
[info] Creating /Users/luogw/temp/hello-world-template/target/scala-2.12/src_managed/test. Read about `ensimeIgnoreMissingDirectories`
[info] Creating /Users/luogw/temp/hello-world-template/src/test/scala-2.12. Read about `ensimeIgnoreMissingDirectories`
[info] Creating /Users/luogw/temp/hello-world-template/src/test/scala. Read about `ensimeIgnoreMissingDirectories`
[info] Creating /Users/luogw/temp/hello-world-template/src/test/java. Read about `ensimeIgnoreMissingDirectories`
[info] Creating /Users/luogw/temp/hello-world-template/target/scala-2.12/src_managed/main. Read about `ensimeIgnoreMissingDirectories`
[info] Creating /Users/luogw/temp/hello-world-template/src/main/scala-2.12. Read about `ensimeIgnoreMissingDirectories`
[info] Creating /Users/luogw/temp/hello-world-template/src/main/java. Read about `ensimeIgnoreMissingDirectories`
[success] Total time: 9 s, completed 2018-6-28 16:37:10

打开工程

使用atom的add project folder功能导入前面创建的工程目录(hello-world-template)
如下图所示：相比使用atom直接编辑源代码文件的情况（命令行的开发环境），现在多个实时的代码高亮与补全等功能的支持。

编码运行

同命令行环境一样，还是需要在sbt

[e-mail] hello-world-template$ sbt
[info] Loading settings from plugins.sbt ...
[info] Loading global plugins from /Users/luogw/.sbt/1.0/plugins
[info] Loading project definition from /Users/luogw/temp/hello-world-template/project
[info] Loading settings from build.sbt ...
[info] Set current project to hello-world (in build file:/Users/luogw/temp/hello-world-template/)
[info] sbt server started at local:///Users/luogw/.sbt/1.0/server/d256dd7eefdec7178cf8/sock
sbt:hello-world> ~run
[info] Compiling 1 Scala source to /Users/luogw/temp/hello-world-template/target/scala-2.12/classes ...
[info] Done compiling.
[info] Packaging /Users/luogw/temp/hello-world-template/target/scala-2.12/hello-world_2.12-1.0.jar ...
[info] Done packaging.
[info] Running Main
Hello, World!
go go go
[success] Total time: 2 s, completed 2018-6-28 17:50:29
1. Waiting for source changes... (press enter to interrupt)
[info] Compiling 1 Scala source to /Users/luogw/temp/hello-world-template/target/scala-2.12/classes ...
[info] Done compiling.
[info] Packaging /Users/luogw/temp/hello-world-template/target/scala-2.12/hello-world_2.12-1.0.jar ...
[info] Done packaging.
[info] Running Main
Hello, World!
go go go
yes
[success] Total time: 1 s, completed 2018-6-28 17:50:55
2. Waiting for source changes... (press enter to interrupt)

IDEA下的Scala开发环境

安装插件

安装插件scala，并重启Scala

创建工程

1.新建项目 File >> New >> Projects

2.新建代码文件

选Object类型（可运行的代码单元）

编码运行

快捷的测试一段代码

* 使用Scala Worksheets来运行一段代码*
启动一个Worksheets的实例是在项目左则面板的src/main/scala目录上右键菜单，然后依序选择 New >> Scala Worksheets, 如下图所示

注：Worksheets左则的代码编程区，右则是代运行结果（同步执行效果，当源代码变更时），类似命中行下的运行效果，估计实现原理也是同样的

参考资料

• scala 官网
• sbt 官网
• sbt-ensime 插件说明
• 
  GETTING STARTED WITH SCALA AND SBT ON THE COMMAND LINE
• GETTING STARTED WITH SCALA IN INTELLIJ
• Using the Atom Editor with Scala
• How to Setup ENSIME in Atom