文章目錄

1. 1. 感想
2. 2. Object type
   1. 2.1. AnyVal
   2. 2.2. AnyRef
   3. 2.3. Other
3. 3. Method
   1. 3.1. 定義
   2. 3.2. 強大的pattern matching
4. 4. Syntactic sugar
5. 5. Eco system

感想

很複雜的語言……很多feature(果然是教授的產物)

除了method 外可以自動估算data type
val r = 1
Object 像一Java 的static method, 不用new object 便可以使用
最後一句預設是回傳值
很多method 沒有side effect

Object type

最頂 Any
其次 AnyVal, AnyRef

AnyVal

AnyVal is primitive datatype in Java
底下有

• Int
• Double
• Flot
• Long
• Short
• Byte
• Char
• Boolean
• Unit (Single Value, ~Void in Java)

AnyRef

底下有AnyObject

• List

Other

Null <- Nothing

Method

定義

method 定義有點像haskell,
名在前, data type 在後
= 之後是回傳數值
def hi(a: String, b: String) = a + b

多種括號
def hi(a: String)(b: String) = a + b
可以這樣呼叫
hi("hi")"Jason"
or
hi("hi") {"jason"}

Accept an function

def goodBye(f: (String) => String, b:String) = f("Jason") + b
goodBye: (f: String => String, b: String)String

functional map on array

val a = Array(1,2,3)
a.map(n => n + 10)
res2: Array[Int] = Array(11, 12, 13)

def test(l : String) = l match {
  case r(_, id) => s"It is a youtube with id: $id"
  case _ => "Not youtube"
}

強大的pattern matching

相比java 麻複的regex……

• r 為regex
• l 為testing string
• _ 指不在乎

val r = """\[url\]https:\/\/(youtu\.be\/|www\.youtube\.com\/)(.+)\[\/url\]""".r.unanchored // anywhere pattern
val l = "[url]https://www.youtube.com/watch?v=Pt7dTw8pm30[/url]"

def test(l : String) = l match {
  case r(_, id) => s"It is a youtube with id: $id"
  case _ => "Not youtube"
}

Syntactic sugar

() 可以當 { }

val echo = Action { request =>
  Ok("Got request [" + request + "]")
}

// is equal to 
val echo = Action.apply(request => {} )

還有implicit
搭少麻煩的variable passing
e.g. 在play framework

def index = Action { implicit request =>
    val str = sayHi("Jason")
    Ok(views.html.index("Your new application is ready." + str))
  }

  private def sayHi(name: String)(implicit req: Request[AnyContent]) = name + ", you can the following content" + req.body

Eco system

type safe activator 太強大了吧…懶人傻瓜包，下載了，就可以在瀏覧器上試玩當中scala各種應用程式template

sbt 不只是用來build, 他還有sbt-launcher.jar
sbt run 會開一個local server 測試用…