Operators

An operator is a symbol or combination of symbols that we can use to check, change, or combine values. We have used operators in most of the examples so far in this book , but we did not specifically call them operators. In this section, we will show how to use most of the basic operators that Swift supports.

Swift supports most standard C operators and also improves them to eliminate several common coding errors. For example, the assignment operator does not return a value, which prevents it from being used where we meant to use the equality operator (==).

Let's look at the operators in Swift.

The assignment operator

The assignment operator initializes or updates a variable.

Prototype:

varA = varB 

Example:

let x = 1 
var y = "Hello" 
a = b 

Comparison operators

The comparison operator returns a Boolean true if the statement is true or a Boolean false if the statement is not true.

Prototypes:

Equality:  varA == varB 
Not equal:  varA != varB 
Greater than:  varA > varB 
Less than:  varA < varB 
Greater than or equal to:  varA >= varB 
Less than or equal to:  varA <= varB 

Example:

2 == 1 //false, 2 does not equal 1 
2 != 1 //true, 2 does not equal 1 
2 > 1  //true, 2 is greater than 1 
2 < 1  //false, 2 is not less than 1 
2 >= 1 //true, 2 is greater or equal to 1 
2 <= 1 //false, 2 is not less or equal to 1 

Arithmetic operators

The arithmetic operators perform the four basic mathematical operations.

Prototypes:

Addition:  varA + varB 
Subtraction:  varA - varB 
Multiplication:  varA * varB 
Division:  varA / varB 

Example:

var x = 4 + 2  //x will equal 6 
var x = 4 - 2  //x will equal 2 
var x = 4 * 2  //x will equal 8 
var x = 4 / 2  //x will equal 2 
var x = "Hello " + "world"  //x will equal "Hello World" 

The remainder operator

The remainder operator calculates the remainder if the first operand is divided by the second operand.

Prototype:

varA % varB 

Example:

var x = 10 % 3  //x will equal 1 
var x = 10 % 2.6  //x will equal 2.2 

Compound assignment operators

The compound assignment operators combine an arithmetic operator with an assignment operator.

Prototypes:

varA += varB 
varA -= varB 
varA *= varB 
varA /= varB 

Example:

var x = 6 
x += 2  //x is equal to 8 
x -= 2  //x is equal to 4 
x *= 2  //x is equal to 12 
x /= 2  //x is equal to 3 

The ternary conditional operator

The ternary conditional operator assigns a value to a variable based on the evaluation of a comparison operator or Boolean value.

Prototype:

(boolValue ? valueA : valueB) 

Example:

var x = 2 
var y = 3 
var z = (y > x ? "Y is greater" : "X is greater")  //z equals    "Y is greater" 

The logical NOT operator

The logical NOT operator inverts a Bboolean value.

Prototype:

varA = !varB 

Example:

var x = true 
var y = !x  //y equals false 

The logical AND operator

The logical AND operator returns true if both operands are true; otherwise it returns false.

Prototype:

varA && varB 

Example:

var x = true 
var y = false 
var z = x && y  //z equals false 

The logical OR operator

The logical OR operator returns true if either of the operands is true.

Prototype:

varA || varB 

Example:

var x = true 
var y = false 
var z = x || y  //z equals true 

For those who are familiar with the C language or similar languages, these operators should look pretty familiar. For those who aren't that familiar with the C operators, rest assured that you will use them enough and they will become second nature.