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

Overview 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...

Life 4 J

初試Scala

感想