Although it’s generally a good idea to use structs or classes for defining your types, sometimes you’ll find yourself using tuples. If this happens to you, it’s quite tedious having to type the full definition of your tuple whenever you want to use it, so the
typealias lets you create a specific name for it:
typealias Name = (first: String, last: String)
Type aliases are also useful when you might want to change the underlying type used for data. For example, you might store a value as a
Float today, but you want to leave open the option to switch to a
Double later on. In this situation, you’d use
typealias like this:
typealias MyValue = Float
You can then go ahead and use
MyValue everywhere in your code, and if you ever choose to change to
Double you can just change the type alias and all your code will update.
Available from iOS 8.0 – learn more in my book Pro Swift
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