For-in loop with collections in Swift - Step-by-Step Execution

Concept Flow - For-in loop with collections

Start with collection

↓

Pick first item

↓

Execute loop body with item

↓

More items?

No→Exit loop

Yes↓

Pick next item

↩Back to Execute loop body

The loop picks each item from the collection one by one and runs the code inside the loop for each item until all items are done.

Execution Sample

Swift

let fruits = ["Apple", "Banana", "Cherry"]
for fruit in fruits {
    print(fruit)
}

This code goes through each fruit in the list and prints its name.

Execution Table

Iteration	fruit value	Action	Output
1	"Apple"	Print fruit	Apple
2	"Banana"	Print fruit	Banana
3	"Cherry"	Print fruit	Cherry
-	-	No more items, exit loop	-

💡 All items in the collection have been processed, loop ends.

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
fruit	nil	"Apple"	"Banana"	"Cherry"	nil

Key Moments - 2 Insights

Why does the loop variable 'fruit' change each time?

Because the loop picks the next item from the collection each iteration, as shown in the execution_table rows 1 to 3.

Does the original collection 'fruits' change during the loop?

No, the collection stays the same; only the loop variable 'fruit' changes to each item, as seen in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'fruit' in iteration 2?

A "Banana"

B "Apple"

C "Cherry"

D nil

💡 Hint

Check the 'fruit value' column in row 2 of execution_table.

At which iteration does the loop finish processing all items?

A After iteration 2

B After iteration 3

C After iteration 1

D Never ends

💡 Hint

Look at the exit_note and the last iteration row in execution_table.

If the collection had 4 items, how many times would the loop run?

A 3 times

B 5 times

C 4 times

D Depends on the code inside the loop

💡 Hint

The loop runs once for each item in the collection, as shown in the concept_flow.

Concept Snapshot

For-in loop syntax:
for item in collection {
    // code using item
}

Behavior:
- Loops over each item in the collection
- 'item' changes each iteration
- Loop ends after last item

Key rule: The collection is not changed by the loop.

Full Transcript

This visual shows how a for-in loop works with collections in Swift. The loop starts by picking the first item from the collection. Then it runs the code inside the loop using that item. After that, it checks if there are more items. If yes, it picks the next item and repeats. If no, it stops. The variable 'fruit' holds the current item and changes each time. The original collection stays the same. The loop runs once for each item in the collection.