Array iteration and enumerated in Swift - Step-by-Step Execution

Concept Flow - Array iteration and enumerated

Start with array

↓

Begin iteration

↓

Get index and element

↓

Use index and element

↓

Move to next element

↓

More elements?

Yes→Repeat

No↓

End iteration

This flow shows how Swift goes through each item in an array, getting both the position (index) and the value (element) to use inside the loop.

Execution Sample

Swift

let fruits = ["Apple", "Banana", "Cherry"]
for (index, fruit) in fruits.enumerated() {
    print("\(index): \(fruit)")
}

This code loops over the fruits array, printing each fruit with its index.

Execution Table

Step	index	fruit	Action	Output
1	0	"Apple"	Print index and fruit	0: Apple
2	1	"Banana"	Print index and fruit	1: Banana
3	2	"Cherry"	Print index and fruit	2: Cherry
4	-	-	No more elements, loop ends	-

💡 After index 2, no more elements in array, loop stops

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
index	-	0	1	2	-
fruit	-	"Apple"	"Banana"	"Cherry"	-

Key Moments - 3 Insights

Why does the index start at 0 instead of 1?

In Swift arrays, counting starts at 0 by design. The execution_table shows index starting at 0 in step 1, which is normal for array positions.

What does enumerated() do exactly?

enumerated() pairs each element with its index. The execution_table rows show both index and fruit together, proving enumerated() gives both.

What happens if the array is empty?

If the array is empty, the loop body never runs. The exit_note explains the loop ends immediately when no elements exist.

Visual Quiz - 3 Questions

Look at the execution_table, what is the fruit at step 2?

A "Banana"

B "Apple"

C "Cherry"

D No fruit

💡 Hint

Check the 'fruit' column in row with Step 2 in execution_table

At which step does the loop stop because there are no more elements?

A Step 3

B Step 4

C Step 2

D Step 1

💡 Hint

Look at the exit_note and the last row in execution_table

If the array had 4 fruits, how many steps would the execution_table have before stopping?

A 4 steps

B 3 steps

C 5 steps

D 6 steps

💡 Hint

Notice the pattern: number of elements + 1 exit step in execution_table

Concept Snapshot

Swift array iteration with enumerated():
- Use for (index, element) in array.enumerated() to get index and value
- Index starts at 0
- Loop runs once per element
- Loop ends when no more elements
- Useful for position-aware processing

Full Transcript

This visual shows how Swift loops over an array using enumerated(). The loop starts with index 0 and the first fruit, then moves to the next index and fruit, printing each pair. When all fruits are processed, the loop ends. The variable tracker shows how index and fruit change each step. Common confusions include why index starts at 0 and what enumerated() does. The quiz checks understanding of the steps and loop end.