Question

this blog曾经有一个有用的Scala Option备忘单，但它似乎已被删除。有没有人保存过它？

Answer 1

注意：senia has provided the whole original post，其中包括介绍和备忘单（在此答案中也如下）。

This blog did!（我没有关联）。有用的备忘单：

flatMap：

// This code is equivalent to:
// option.flatMap(foo(_))
option match {
  case None => None
    case Some(x) => foo(x)
}

弄平：

// This code is equivalent to:
// option.flatten
option match {
  case None => None
    case Some(x) => x
}

图：

// This code is equivalent to:
// option.map(foo(_))
option match {
  case None => None
    case Some(x) => Some(foo(x))
}

的foreach：

// This code is equivalent to:
// option.foreach(foo(_))
option match {
  case None => {}
  case Some(x) => foo(x)
}

isDefined：

// This code is equivalent to:
// option.isDefined
option match {
  case None => false
    case Some(_) => true
}

的isEmpty：

// This code is equivalent to:
// option.isEmpty
option match {
  case None => true
    case Some(_) => false
}

的forall：

// This code is equivalent to:
// option.forall(foo(_))
option match {
  case None => true
    case Some(x) => foo(x)
}

存在：

// This code is equivalent to:
// option.exists(foo(_))
option match {
  case None => false
    case Some(x) => foo(x)
}

否则容易：

// This code is equivalent to:
// option.OrElse(foo)
option match {
  case None => foo
    case Some(x) => Some(x)
}

getOrElse：

// This code is equivalent to:
// option.getOrElse(foo)
option match {
  case None => foo
    case Some(x) => x
}

toList：

// This code is equivalent to:
// option.toList
option match {
  case None => Nil
    case Some(x) => x :: Nil
}

coflatMap *：

// This code is equivalent to:
// option.coflatMap(foo(_))
option match {
  case None => None
  case Some(_) => Some(foo(option))
}

重复*：

// This code is equivalent to:
// option.duplicate
option match {
  case None => None
  case Some(_) => Some(option)
}

*：不幸的是，coflatMap和duplicate不是标准库的一部分。您需要自己编写或使用Scalaz。

摘录结束

Answer 2

您可以在archive.org上获得完整版（带介绍）。