更換代表團蛋糕

Question

在我上一類堆疊功能與代表團

trait Backend { 
    def product(id: Int): String 
} 

class MyBackend extends Backend { 
    def product(id: Int) = "My product" 
} 

class LoggingBackend(underlying: Backend) extends Backend { 
    override def product(id: Int) = { 
    println(s"get product $id") 
    underlying.product(id) 
    } 
} 

class CachingBackend(underlying: Backend) extends Backend { /* ... */ } 

是否有可能像這樣的東西替換此代碼的那一刻？

trait Logging { 
    this : Backend => 

    def product(id: Int) = { 
    println(s"get product $id") 
    /* Don't know what to write here */ 
    } 
} 

class MyLoggingBackend extends MyBackend with Logging 

Answer 1

你只需要改變Logging：

trait Logging extends Backend { 
    abstract override def product(id: Int) = { 
    println(s"get product $id") 
    super.product(id) 
    } 
}