iOS 11 Programming Fundamentals with Swift: Swift, Xcode, and Cocoa Basics

Encapsulating function-calling in a function can reduce repetition and opportunity for error. Moreover, the other function may call the parameter function in some special way; for example, it might call it after doing other things, or at some later time.

Eventually, you may want to do some further reading on effective planning and construction of the architecture of an object-based program. I recommend in particular two classic, favorite books. Refactoring, by Martin Fowler (Addison-Wesley, 1999), describes why you might need to rearrange what methods belong to what classes (and how to conquer your

Anonymous Functions

Unfortunately, there’s a hole in the Swift language: there’s no way to convert an array into a comma-separated list of arguments (comparable to splatting in Ruby). If what you’re starting with is an array of some type, you can’t use it where a variadic of that type is expected.

The top-level namespaces are modules. By default, your app is a module and hence a namespace; that namespace’s name is, roughly speaking, the name of the app.

We may summarize the nature of objects in two phrases: encapsulation of functionality, and maintenance of state.

In Swift, every noun is an object, and every verb is a message.

To sum up: A class declaration defines a namespace. This namespace requires that other objects use an extra level of dot-notation to refer to what’s inside the namespace, but other objects can still refer to what’s inside the namespace; the namespace does not, in and of itself, close any doors of visibility. The private keyword lets you close those

So Swift has three kinds of object type: classes, structs, and enums. I like to refer to these as the three flavors of object type.