@boat asks:
what is does the .value mean in
let mysteryGirls = dict.filter { $0.value }
Think about what a printed dictionary is. You have a book that has lots of words in it. Each word has a related definition.
For example if you looked up Boat in a dictionary, you'd see the definition
BOAT: A large hole in the water into which one pours money.
In Swift, a dictionary follows a similar concept. In @rooster's example, he created a dictionary named dict. (Pick a better name, svp!)
Swift dictionaries follow a <Key, Value> design. In his example, the KEY is a person's name. The VALUE is boolean representing gender.
In a printed dictionary, the KEY is the word you're looking up, and the VALUE is the word's definition.
When you retrieve items from a Swift dictionary, you can examine the item's KEY, its VALUE, or both. In @rooster's example, he's going through each item in the dictionary, and performing a filter.
In Swift $0 is a placeholder for a dictionary entry. It contains BOTH the KEY and the VALUE.
$0.value is the syntax to ask Swift to examine just the VALUE portion of the dictionary item passed to the filter.
Time for @boat to brush up on Swift dictionaries. Please review @twostraw's 60 second video:
Swift Dictionaries