如何理解Option作爲模式匹配的操作？

Question

this blog曾經是一個有用的Scala選項備忘單，但似乎已被刪除。有沒有人保存過它？

Answer 1

結束時，你可能會得到archive.org完整版（含引進）。

Link to archive version.

Answer 2

注意：senia has provided the whole original post，其中包括介紹和cheatsheet（這也是下面在這個答案）。

This blog did!（我是無黨派的）。不斷有幫助的cheatsheet：

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flatMap：

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

扁平化：

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

地圖：

// 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) 
} 

否則容易：

// 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)) 
} 

複製*：

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

*：不幸的是，coflatMap和duplicate不是標準庫的一部分。您需要自己寫或使用Scalaz。

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