Programming Basics

Comments

// This is a comment
/* This is a multiline comment
   They can not be nbested! */

Comment Links

// MARK: Test appears in Xcode selector
// TODO: Write your todo here
// FIXME: Write your bug here (or fix is directly)

Importing namespaces

using System; // import namespace System
Console.WriteLine(x); // use function of namespace System

System.Console.WriteLine(x); // using without importin namespace

Types

For a complete guide to 64-bit changes, please see the transition document.

Default Swift Types

C-Types vs Swift Types

From the docs

Operators

Swift supports most standard C operators and improves several capabilities to eliminate common coding errors.

Arithmetic operators (+, -, *, /, % and so forth) detect and disallow value overflow, to avoid unexpected results when working with numbers that become larger or smaller than the allowed value range of the type that stores them.

Arithmetic Operators

Comparative Operators

Assignment Operators

Increment and Decrement Operators

++x //increments variable **before** returning it's value
x-- //increments variable **after** returning it's value

Logical Operators

Range Operators

for index in 1..<3 {} // 1 to 3 excluding 3
for index in 1...3 {} // 1 to 3 inluding 3

Bitwise Operators

Overflow and Underflow Operators

Typically, assigning or increment an integer, float, or double past it's range would result in a run-time error. However, if you'd instead prefer to safely truncate the number of available bits, you can opt-in to have the variable overflow or underflow using the following operators:

Example for unsigned integers (works similarly for signed):

var willOverflow = UInt8.max       // willOverflow = 255
willOverflow = willOverflow &+ 1   // willOverflow = 0

var willUnderflow = UInt8.min      // willUnderflow = 0
willUnderflow = willUnderflow &- 1 // willUnderflow = 255

Another example to show how you can prevent dividing by zero from resulting in infinity:

let x = 1
let y = x &/ 0 // Division by zero y = 0

Other Operators