【Swift 60秒】97 - Optionals: Summary

0x00 Lesson

You’ve made it to the end of the tenth part of this series, so let’s summarize:

1. Optionals

   let us represent the absence of a value in a clear and unambiguous way.
2. Swift won’t let us use optionals without unwrapping them, either using

   if let

   or using

   guard let

   .
3. You can force unwrap optionals with an exclamation mark, but if you try to force unwrap nil our code will

   crash

   .
4. Implicitly unwrapped optionals don’t have the safety checks of regular optionals.
5. You can use

   nil coalescing

   to unwrap an optional and provide a default value if there was nothing inside.
6. Optional chaining lets us write code to manipulate an optional, but if the optional turns out to be empty the code is ignored.
7. You can use

   try?

   to convert a throwing function into an optional return value, or

   try!

   to crash if an error is thrown.
8. If you need your initializer to fail when it’s given bad input, use

   init?()

   to make a failable initializer.
9. You can use

   typecasting

   to convert one type of object to another.

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