Result

Result 与 Option 相似，但表示操作成功或失败，且每个操作的类型不同。这类似于表达式练习中定义的 Res，但是一个泛型：Result<T, E>，其中 T 用于 Ok 变体，E 出现在 Err 变体中。

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Speaker Notes

 This slide should take about 10 minutes.
  • 与 Option 方法相同，成功值位于 Result 方法内部， 开发者必须显示提取成功值。因此，建议进行错误检查。在绝不应出现错误的情况下， 可以调用 unwrap() 或 expect() 方法，这也是一种开发者意向信号。
  • Result documentation is a recommended read. Not during the course, but it is worth mentioning. It contains a lot of convenience methods and functions that help functional-style programming.
  • Result is the standard type to implement error handling as we will see on Day 4.