Understanding closures
A closure, like a function, contains a sequence of instructions and can take arguments and return values. However, closures don't have names. The sequence of instructions in a closure is surrounded by curly braces ({ }), and the in keyword separates the arguments and return type from the closure body.
Closures can be assigned to a constant or variable, so they're handy if you need to pass them around inside your program. For instance, let's say you have an app that downloads a file from the internet, and you need to do something to the file once it has finished downloading. You can put a list of instructions to process the file inside a closure and have your program execute it once the file finishes downloading. You'll see how closures are used in Chapter 16, Getting Started with MapKit.
Important Information
To learn more about closures, visit https://docs.swift.org/swift-book/LanguageGuide/Closures.html.
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