switch and case

Sprout gives each streak length its own badge: nothing at 0, "Seedling" for the first week, a special badge on days 7, 14 and 21, and "Tree" beyond. A long if/else if chain can do it, but switch reads like the table in the design notes.

The rule

switch must cover every value; the first matching case runs, then stops.

The rules:

• Exhaustive. Every possible value must match some case. An Int has an enormous number of possible values, so you need default as a catch-all.
• First match wins. Swift checks cases top to bottom and runs only the first that matches.
• No falling through. When a case finishes, the whole switch ends. You do not write break after each case. (If you truly want to run the next case too, the keyword fallthrough does it.)
• Every case needs a statement. For "do nothing", write break.

Cases can match more than single values:

• several values: case 7, 14, 21:
• ranges: case 1...6:
• extra conditions: case let n where n > 100:
• strings and, later, enums: case "Read":

Like if, a switch can produce a value:

The shortcut

Read a switch like a list of doors, tried from the top. Take the value, walk down, and go through the first door it fits. Nothing after that door matters.

Drills

Answer fast — trust the rule.

Remember

• switch must cover every value; the first matching case runs, then stops.
• Walk the doors from the top: specific cases before wide ranges.
• No break needed after cases; default catches the rest.