Great work! We’ve expanded on our understanding of structures and properties and learned about access control, adding a lot of useful tools to our Swift toolbelt. Here are the key points we covered in this lesson:

• The boundaries for access control are modules, source files, and structs.
  • Public is the most permissive and allows access between modules. (useful for SDKs and frameworks)
  • Internal is the default level and allows access anywhere within a module.
  • File private allows access within a source file.
  • Private can only be used within the scope of a struct. (least permissive)
• Private properties are defined using the private syntax.
  • Memberwise initializers can’t access private properties, so you need to use default values, make them optional, or use the init method.
• Private methods use the same syntax as private properties and can only be called within the scope of the struct that defines them.
• Computed properties aren’t stored values, rather they are derived from other stored properties.
  • Can be read-only. (only have getter method)
  • Can set them, in which case you change the underlying properties from which they are derived.
• Property observers are built in methods that get called when properties are set.
  • didSet gives us the old value.
  • willSet gives us the new value.
• Properties can have a more restricted access level to set vs. get.
• Type properties are defined independently from any particular instance of a structure.