If and if-else statements in Swift - Step-by-Step Execution

Concept Flow - If and if-else statements

Start

↓

Evaluate condition

↓

Execute if-block

↓

Continue

↓

Check if else-block exists?

↓

Execute else-block

↓

Continue

↓

Continue

The program checks a condition. If true, it runs the if-block. If false and else-block exists, it runs else-block. Then it continues.

Execution Sample

Swift

let number = 7
if number % 2 == 0 {
    print("Even")
} else {
    print("Odd")
}

Checks if number is even or odd and prints the result.

Execution Table

Step	Condition	Result	Branch Taken	Output
1	number % 2 == 0	7 % 2 == 0 → 1 == 0 → false	else-block	Odd
2	End of if-else	No more conditions	Exit

💡 Condition is false, else-block runs, then execution ends.

Variable Tracker

Variable	Start	After Step 1	Final
number	7	7	7

Key Moments - 2 Insights

Why does the else-block run when the condition is false?

Because the condition in the if statement is false (see execution_table step 1), the program skips the if-block and runs the else-block instead.

What happens if there is no else-block and the condition is false?

The program skips the if-block and continues without running any code inside the if or else blocks (not shown in this example).

Visual Quiz - 3 Questions

Look at the execution table, what is the condition result at step 1?

A true

B undefined

C false

D error

💡 Hint

Check the 'Result' column in execution_table row 1.

At which step does the else-block run?

A Step 1

B Step 2

C No else-block runs

D Before step 1

💡 Hint

Look at the 'Branch Taken' and 'Output' columns in execution_table row 1.

If number was 8, how would the output change?

A "Odd"

B "Even"

C No output

D Error

💡 Hint

Think about the condition number % 2 == 0 with number = 8.

Concept Snapshot

if condition {
  // code runs if condition is true
} else {
  // code runs if condition is false
}

- Condition is checked once.
- If true, if-block runs.
- Else-block runs only if condition is false.
- Else-block is optional.

Full Transcript

This visual shows how if and if-else statements work in Swift. The program starts by checking a condition. If the condition is true, it runs the code inside the if-block. If the condition is false and there is an else-block, it runs the else-block code instead. Then the program continues after the if-else. For example, checking if a number is even or odd uses this logic. The execution table shows the condition check, the branch taken, and the output printed. The variable tracker shows the value of the number throughout. Key moments clarify why the else-block runs when the condition is false and what happens if there is no else-block. The quiz asks about condition results, when the else-block runs, and how changing the number affects output. The snapshot summarizes the syntax and behavior simply.