斯卡拉繼承：爲什麼我必須定義我的類是抽象的？

Question

class inheritance 
{ 
    def a() 
    println("Version 1") 
} 

class inheritance1 
{ 
    def b() 
    println("version 2") 
} 

class inheritance2 extends inheritance 
{ 
    def c() 
    println("version 3") 
} 

class inheritance3 extends inheritance2 
{ 
    def d() 
    println("version 4") 
} 

object inherited 
{ 
    def main(args: Array[String]) 
    { 
    var obj = new inheritance3 
    obj.d 
    obj.c 
    } 
} 

它拋出了幾個錯誤：

class inheritance needs to be abstract since method a is not defined 

class inheritance1 needs to be abstract since method b is not defined 

class inheritance2 needs to be abstract since it has two unimplemented members 

class inheritance3 needs to be abstract since it has two unimplemented members 

Answer 1

喜歡的東西

def a() 
println("foo") 

聲明一個未定義的方法a，它沒有任何參數和返回Nothing，然後打印出一個字符串。

def a() = println("foo") 

或

def a() { 
    println("foo") 
} 

或

def a() = 
    println("foo") 

定義的方法a，打印出的字符串並返回一個Unit。