Swift - If-else Statement

The if-else statement in Swift is a fundamental control flow structure that allows code to execute based on whether a specific condition is true or false.

Syntax:

The general structure of an if-else statement is as follows:

if condition {
    // Code to execute if the condition is true
} else {
    // Code to execute if the condition is false
}

Example:

Let's consider a simple example where we check if a number is even or odd:

let number = 5

if number % 2 == 0 {
    print("The number is even.")
} else {
    print("The number is odd.")
}

// Output: The number is odd.

In this example:

The if condition checks if the remainder of the number divided by 2 is zero (meaning the number is even).
If the condition is true, it prints "The number is even."
If the condition is false (as is the case with the number 5), the code inside the else block executes, printing "The number is odd."

Notes:

The else block is optional. You can have an if statement without an else:

if condition {
    // Code to execute if the condition is true
}

Parentheses () around conditions are optional in Swift. So, both if condition {...} and if (condition) {...} are valid, but the former is more idiomatic in Swift.
Always ensure that the condition inside the if statement returns a boolean (true or false). If it doesn't, the Swift compiler will raise an error.
The if-else statement can be expanded further using else if to check for multiple conditions, which was discussed in the previous answer on the if-else-if statement.

How to use if-else in Swift programming:
- Description: The if-else statement in Swift allows you to conditionally execute code blocks based on a given condition.
- Code:
```
let number = 10

if number > 0 {
    print("Number is positive")
} else {
    print("Number is non-positive")
}
```
Conditional statements in Swift with if-else:
- Description: if-else is a fundamental conditional statement in Swift, allowing you to handle alternative code paths.
- Code:
```
let temperature = 25

if temperature > 30 {
    print("It's hot!")
} else {
    print("It's not too hot.")
}
```
Handling multiple conditions in if-else in Swift:
- Description: Multiple conditions can be handled using chained if-else statements.
- Code:
```
let grade = 85

if grade >= 90 {
    print("A")
} else if grade >= 80 {
    print("B")
} else {
    print("C or below")
}
```

Nested if-else statements in Swift:

Description: if-else statements can be nested to handle more complex conditions.

Code:

let age = 25

if age >= 18 {
    print("You are an adult")
    if age >= 21 {
        print("You can buy alcohol")
    }
} else {
    print("You are a minor")
}

Using logical operators in Swift if-else:

Description: Logical operators (&&, ||, !) can be used to combine conditions in if-else statements.

Code:

let isWeekend = true
let hasPartyInvitation = false

if isWeekend || hasPartyInvitation {
    print("Let's party!")
} else {
    print("No party today.")
}

Swift if-else statement with optionals:

Description: Optionals can be safely unwrapped using if-else statements with optional binding (if let or guard let).

Code:

let optionalValue: Int? = 42

if let unwrappedValue = optionalValue {
    print("Optional has a value: \(unwrappedValue)")
} else {
    print("Optional is nil")
}

Conditional expressions and ternary operator in Swift:
- Description: Ternary conditional operator (a ? b : c) provides a concise way to express if-else conditions.
- Code:
```
let isSunny = true

let weatherMessage = isSunny ? "It's sunny!" : "It's not sunny."
print(weatherMessage)
```