Maybe It’s There, Maybe It Isn’t: Optionals
A few times so far we’ve seen our log messages include the term “optional,” a behavior we’ve put off explaining until now. But it’s time to deal with it, because optionals are one of Swift’s defining features. Create a new playground called OptionalsPlayground and delete the "Hello, playground" line, as usual.
We’ll start by adding the sizeInMm dictionary from a few sections back, since that’s something that started giving us this “optional” stuff.
| | let sizeInMm = [ |
| | "iPhone 6s": 138.1, |
| | "iPhone 6s Plus" : 158.1, |
| | "iPad Air 2" : 240.0] |
Looking at this, we can see that sizeInMm["iPhone 6s"] should evaluate to 138.1, which is a
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