scala - Scala 检查 ListBuffer[MyType] 是否包含一个元素

Question

我有两个班级：

class Item(val description: String, val id: String) 

class ItemList {
  private var items : ListBuffer[Item] = ListBuffer()
}

如何检查项目是否包含一项 description=x 和 id=y 的项目？

Answer 1

那将是

list.exists(item => item.description == x && item.id == y)

如果您还equals为您的课程实现（或者甚至更好，让它case class自动执行），您可以将其简化为

case class Item(description: String, id: String)
 // automatically everything a val, 
 // you get equals(), hashCode(), toString(), copy() for free
 // you don't need to say "new" to make instances

list.contains(Item(x,y))

Answer 2

像这样的东西：

def containsIdAndDescription(id: String, description: String) = {
   items.exists(item => item.id == id && item.description == description )
}

Answer 3

也许还可以考虑这些方法：

//filter will return all elements which obey to filter condition

list.filter(item => item.description == x && item.id == y)

//find will return the fist element in the list

list.find(item => item.description == x && item.id == y)