Choose the Correct Collection

Learning to use the most appropriate class or object for the task at hand is fundamental to writing efficient code. This is especially true when dealing with collections.

Happily, there’s a document named Collections Programming Topics on Apple’s Developer Library that explains in detail the differences between the available classes, as well as which situations suit each class. It’s a must read document for anyone looking to work with collections.
TLDR? Here’s a quick synopsis of the most common collection types:

  • Arrays: Ordered list of values. Quick lookup by index, slow to lookup by value, slow to insert/delete.
  • Dictionaries: Store key/value pairs. Quick lookups by key.
  • Sets: Unordered list of values. Quick lookup by value, quick to insert/delete.

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