Switch with compound cases in Swift - Step-by-Step Execution

Concept Flow - Switch with compound cases

Start: value to check

↓

Switch statement begins

↓

Check first case

↓

Execute case

↓

End switch

↓

Default case

↓

Execute default

↓

End switch

The switch checks the value against each case, including compound cases separated by commas, and executes the matching case block.

Execution Sample

Swift

let letter = "a"
switch letter {
case "a", "e", "i", "o", "u":
    print("Vowel")
default:
    print("Consonant")
}

This code checks if the letter is a vowel using a switch with compound cases.

Execution Table

Step	Condition Checked	Result	Branch Taken	Output
1	letter == "a" or letter == "e" or letter == "i" or letter == "o" or letter == "u"	True (letter is "a")	case "a", "e", "i", "o", "u"	Vowel
2	Switch ends after matching case	N/A	Exit switch	N/A

💡 Matching case found at step 1, switch exits after executing that case.

Variable Tracker

Variable	Start	After Step 1	Final
letter	"a"	"a"	"a"

Key Moments - 2 Insights

Why does the switch not check other cases after finding a match?

Because in Swift, once a matching case is found, the switch exits immediately as shown in execution_table step 2.

How do compound cases work in the switch?

Compound cases use commas to list multiple values in one case, so if the value matches any of them, that case runs (see execution_table step 1).

Visual Quiz - 3 Questions

Look at the execution table, what is the output at step 1?

A Error

B Consonant

C Vowel

D No output

💡 Hint

Check the 'Output' column in execution_table row 1.

At which step does the switch stop checking cases?

A Step 1

B Step 2

C After default case

D Never stops

💡 Hint

Look at the 'Branch Taken' and 'Exit switch' note in execution_table step 2.

If letter was "b", what case would run?

A default

B case "a", "e", "i", "o", "u"

C No case runs

D Error

💡 Hint

If no compound case matches, switch runs the default case.

Concept Snapshot

switch value {
  case val1, val2, val3:
    // runs if value matches any listed
  default:
    // runs if no case matches
}
- Compound cases use commas to check multiple values
- Switch exits after first match
- Default handles unmatched values

Full Transcript

This example shows how a Swift switch statement uses compound cases separated by commas to check if a value matches any of several options. The switch checks each case in order. When it finds a match, it runs that case's code and then exits the switch immediately. If no cases match, the default case runs. Here, the letter "a" matches the first compound case, so "Vowel" is printed and the switch ends.