Comments and Semicolons
Three weeks from now you will open Sprout's streak code and wonder why a missed day on a Sunday does not reset the streak. A one-line comment written today answers that in a second. Comments are notes for humans; the compiler ignores them. Semicolons, meanwhile, are something Swift mostly lets you forget.
The rule
Comments explain why; semicolons only join two statements on one line.
Swift has three comment styles:
// A single-line comment runs to the end of the line.
/* A block comment can run
over several lines. */
/// Returns the streak after today's check-in.
/// Shown in Xcode's Quick Help for this function.
func nextStreak(from streak: Int) -> Int {
streak + 1
}//is for short notes./* */wraps several lines. In Swift, block comments can nest: a/* */inside another/* */is fine, which makes it safe to comment out code that already contains one.///is a documentation comment. Xcode shows it when you Option-click the name it sits above.
Good comments say why, not what. streak += 1 // add one to streak repeats the code. // Weekends are optional in Sprout, so a Sunday miss keeps the streak saves the next reader real time.
Semicolons are optional at the end of a line. Swift code almost never uses them. They are needed only to put two statements on the same line:
let done = 3; let goal = 5The shortcut
For comments, ask "could the reader get this from the code alone?" If yes, delete the comment. If no, it is worth keeping. For semicolons, ask "are there two statements on this line?" Only then is one required.
var streak = 0;One statement on the line. The semicolon is legal but pointless. Remove it.
Nesting is a small Swift nicety: in C, a */ inside a block comment ends it early. In Swift, the comments pair up correctly.
Drills
Answer fast — trust the rule.
When is a semicolon required in Swift?
Which comment style appears in Xcode's Quick Help?
Which is the more useful comment?
What happens when a /* */ comment contains another /* */ comment in Swift?
Remember
- Comments explain why; semicolons only join two statements on one line.
//for notes,/* */for blocks (they nest),///for Quick Help docs.- If the code already says it, the comment should go.