Ruby: Control Structure

Conditions

• if-elsif-else(basic):
  • basic condition control structure, will do anything you want.
  • trick1: when you assign a value to a variable behind if
    • that variable can only be used in the multiline scheme.
    • that variable cannot be used in the single line scheme.
  • trick2: when you define a variable inside the conditional block.
    • you can use it outside the conditional block
    • when the condition is false, outside variable value is nil.
    • both single line and multiline schemes can use this feature.
• case-when-else(switch):
  • has clear structure than the basic if-else structure.
  • internally use the ruby triple equal operator === to compare.
  • a === b means "if 'a' describe a set, would 'b' be a member of that set?"
    • when range and element: (1..5) === 3
    • when class and class: Object === String
    • when class and object: Object === 'string'
    • when regex and string: /foo/ === 'foobar'
    • you can also rewrite object === method
• ternary-operator(terse):
  • only use one line code, look so pretty :P_
  • suit with simple statement, shouldn't be too complex.
  • also use for assignment with condition: a = condition ? b : c
• && (and) vs || (or):
  • a && b can convert to: b if a
  • a || b can convert to: b if not a
  • assign with default value: x = a || b
  • assign if not assigned before: x ||= c

Loops

• iterators:
  • (basic) each, select, map, reduce...
  • (numbers) times, upto, downto, step...
• traditional-loop:
  • loop: infinite loop, use break to stop it.
    • use case: generate unique random keys.
• control-keywords:
  • break: says quit immediately.
  • next: says loop immediately.
  • redo: says redoes that same loop over again.
  • retry: says starts the whole loop over from the beginning.