Swift Conditional Statements

Conditional statements execute programs based on one or more set conditions. When a condition is true, the specified statement(s) are executed; when the condition is false, other specified statement(s) are executed.

The execution flow of conditional statements can be simply understood from the following diagram:

Swift provides the following types of conditional statements:

Statement Description

if statement

 if statementConsists of a boolean expression and one or more executable statements.

if...else statement

 if statementcan be followed by an optionalelse statement, else statementExecuted when the boolean expression is false.

if...else if...else statement

 ifcan be followed by an optionalelse if...elsestatement,else if...elseThe statement is often used for multiple condition judgments.

Nested if statement

 You caniforelse ifnestiforelse ifstatements.

switch statement

 The switch statement allows testing a variable against multiple values.

? : Operator

We have already explained in previous chaptersthe conditional operator ? :, which can be used to replaceif...elsestatements. Its general form is as follows:

Exp1 ? Exp2 : Exp3;

Here, Exp1, Exp2, and Exp3 are expressions. Note the usage and position of the colon.

The value of the ? expression is determined by Exp1. If Exp1 is true, the value of Exp2 is evaluated, and the result is the value of the entire ? expression. If Exp1 is false, the value of Exp3 is evaluated, and the result is the value of the entire ? expression.

Other Extensions