While loop in Swift - Step-by-Step Execution

Concept Flow - While loop

Initialize variable

↓

Check condition

|Yes↓

Execute loop body

↓

Update variable

Back to Check↓

Exit loop

↩Back to Check

The while loop starts by checking a condition. If true, it runs the loop body, updates variables, then checks again. It stops when the condition is false.

Execution Sample

Swift

var count = 1
while count <= 3 {
    print(count)
    count += 1
}

This code prints numbers 1 to 3 using a while loop that runs while count is less or equal to 3.

Execution Table

Step	count	Condition (count <= 3)	Action	Output
1	1	true	print 1, count = 2	1
2	2	true	print 2, count = 3	2
3	3	true	print 3, count = 4	3
4	4	false	exit loop

💡 count becomes 4, condition 4 <= 3 is false, loop stops

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
count	1	2	3	4	4

Key Moments - 2 Insights

Why does the loop stop when count is 4 even though the loop body has a print statement?

Because the condition count <= 3 is checked before the loop body runs (see step 4 in execution_table). When count is 4, the condition is false, so the loop exits without printing.

What happens if we forget to update count inside the loop?

The condition will always be true (count stays 1), causing an infinite loop. The execution_table shows count increasing each step to avoid this.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of count at step 3?

A 2

B 3

C 4

D 1

💡 Hint

Check the 'count' column in execution_table row for step 3.

At which step does the condition become false and the loop stops?

A Step 4

B Step 2

C Step 3

D Step 1

💡 Hint

Look at the 'Condition' column in execution_table to find when it is false.

If we change the initial count to 4, what will happen to the loop?

A It will run infinitely

B It will print 4 once and stop

C It will not print anything and stop immediately

D It will print numbers from 4 to 3

💡 Hint

Refer to variable_tracker and condition check in execution_table; condition is false if count starts at 4.

Concept Snapshot

Swift while loop syntax:
while condition {
    // code to repeat
}

- Checks condition before each loop
- Runs loop body only if condition is true
- Stops when condition is false
- Remember to update variables inside loop to avoid infinite loops

Full Transcript

This visual execution shows how a Swift while loop works. We start with a variable count set to 1. The loop checks if count is less or equal to 3. If yes, it prints count and increases it by 1. This repeats until count becomes 4, when the condition fails and the loop stops. The execution table tracks each step, showing count values, condition results, actions, and outputs. The variable tracker shows how count changes after each iteration. Key moments explain why the loop stops before printing when condition is false and the importance of updating count to avoid infinite loops. The quiz tests understanding of count values at steps, when the loop stops, and effects of changing initial count.