3. Optionals?!
nil happens. When dictionary lookups fail, when instance properties are case dependent, when asynchronous operations have not completed, when failable initializers cannot create instances, and in dozens of other situations where values may or may not have been set, Swift may return nil instead of some other more concrete content. Swift provides nil as a powerful tool for expressing situations in which values are unavailable for use.
Swift differentiates these “no content” scenarios from error handling. In error handling, control flow changes to offer failure mitigation and reporting. With nil, a value-of-no-value represents an absence of data. It offers a testable placeholder to be used when no data is otherwise available.
Unlike ...
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