Swift Live Reference

Within these castle walls be forged Mavens of Computer Science ...

— Merlin, The Coder

Comments

Comments are used by humans to document code for other humans. They have no effect on the program itself.

Single-line comments

// single-line comments begin with two slashes

Multi-line comments

/* multi-line comments begin with slash-star
   and continue 
   and continue
   until a closing star-slash */

Control Structures

Control structures are used to alter the otherwise sequential flow of a program.

Conditionals

Conditionals are used to execute a segment of code based upon a condition being met.

if

if n < 10 {
    print("n is less than 10")
}

else

if n < 10 {
    print("n is less than 10")
} else {
    print("n is not less than 10")
}

switch

switch n {
    case 0:
        print("n is zero")
    case 1:
        print("n is one")
    default:
        print("n is neither one nor zero")
}

Loops

Loops are used to repeat a segment of code until a condition is met.

for

for n in 0 ..< 10 {
    print(n)
}

while

while n < 10 {
    n += 1
}

repeat while

repeat {
    n += 1
} while n < 10