Swift - Fallthrough Statement

In Swift, control flow in a switch statement is defined differently than in many traditional C-like languages. In most C-based languages, you might expect execution to "fall through" to subsequent case labels in a switch statement unless you explicitly break out of the current case. However, Swift's switch cases don't fall through by default. This design choice helps prevent common errors from unintentional fallthroughs.

Still, Swift provides the fallthrough keyword for cases where you specifically want a case to fall through to the next one.

Usage of `fallthrough`:

Here's an example demonstrating the use of fallthrough:

var description = ""
var number = 3

switch number {
case 1:
    description += "One "
    fallthrough
case 2:
    description += "Two "
    fallthrough
case 3:
    description += "Three "
default:
    break
}

print(description)  // Outputs: "Two Three "

In the example above:

When number is 1: The output will be "One Two Three ".
When number is 2: The output will be "Two Three ".
When number is 3: The output will be "Three ".

If we had not used fallthrough, the switch statement would simply match the case for the value of number and execute only that case's code block, without continuing to subsequent cases.

Caution:

Use fallthrough judiciously and only when you specifically want a fallthrough behavior. It can make the code harder to understand if overused or used without a clear intent.
Unlike many C-based languages, the fallthrough keyword in Swift does not check the next case's conditions. It simply continues the execution into the next case block. So, be careful, as this can lead to unintended behavior if you're expecting traditional fallthrough semantics.

In summary, Swift's switch statement is designed to be safer by preventing unintended fallthroughs. However, when necessary, the fallthrough keyword allows for manual fallthrough behavior.

How to use fallthrough in Swift switch cases:

Description: fallthrough is a keyword in Swift used within a switch statement to transfer control to the next case, allowing sequential execution of multiple cases.

Code:

let number = 2
var description = ""

switch number {
case 1:
    description += "One "
    fallthrough
case 2:
    description += "Two "
    fallthrough
case 3:
    description += "Three "
default:
    break
}

print(description) // Outputs: "One Two Three "

Swift switch statement fallthrough example:

Description: The fallthrough keyword is used in a switch statement to execute code in the current case and then fall through to the next one.

Code:

let grade = "B"
var feedback = "Your grade is "

switch grade {
case "A":
    feedback += "Excellent!"
case "B":
    feedback += "Good. "
    fallthrough
case "C":
    feedback += "Keep it up."
default:
    break
}

print(feedback) // Outputs: "Your grade is Good. Keep it up."

Fallthrough vs. break in Swift switch cases:

Description: fallthrough continues to the next case without checking its condition, while break exits the switch statement.

Code:

let number = 2
var description = ""

switch number {
case 1:
    description += "One "
    fallthrough
case 2:
    description += "Two "
    break // Without break, it would continue to the next case
case 3:
    description += "Three "
default:
    break
}

print(description) // Outputs: "One Two"

Using fallthrough for sequential case execution in Swift:

Description: fallthrough is useful when you want to execute code sequentially for multiple cases in a switch statement.

Code:

let day = 3
var message = "Today is "

switch day {
case 1:
    message += "Monday. "
    fallthrough
case 2:
    message += "Tuesday. "
    fallthrough
case 3:
    message += "Wednesday. "
default:
    break
}

print(message) // Outputs: "Today is Monday. Tuesday. Wednesday."

Nested switch statements and fallthrough in Swift:

Description: fallthrough can be used in nested switch statements to control the flow within the nested cases.

Code:

let outerSwitch = 1
let innerSwitch = 2
var result = ""

switch outerSwitch {
case 1:
    result += "One "
    switch innerSwitch {
    case 1:
        result += "Nested One "
        fallthrough
    case 2:
        result += "Nested Two "
    default:
        break
    }
default:
    break
}

print(result) // Outputs: "One Nested One Nested Two"

Swift - Fallthrough Statement

Usage of fallthrough:

Caution:

Usage of `fallthrough`: