Swift Conditional Statements

A conditional statement tells your program to take a specific action when a certain condition is true. Without conditionals, every program would do the same thing every time — with them, programs can make decisions.

The Traffic Light Analogy

┌─────────────────────────────────────────────┐
│          Traffic Light Decision             │
│                                             │
│  IF light is Green  → Drive                 │
│  ELSE IF light is Yellow → Slow down        │
│  ELSE (light is Red)    → Stop              │
│                                             │
│  Your code works exactly the same way.      │
└─────────────────────────────────────────────┘

The if Statement

let temperature = 38

if temperature > 35 {
    print("It is very hot today.")
}

Swift checks whether temperature > 35 is true. Since 38 is greater than 35, the message prints. If the condition were false, the block would be skipped entirely.

The if-else Statement

let score = 45

if score >= 50 {
    print("You passed.")
} else {
    print("You need to improve.")
}

When the condition is false, the else block runs. Exactly one of the two blocks always executes.

The if-else if-else Chain

let marks = 72

if marks >= 90 {
    print("Grade: A")
} else if marks >= 75 {
    print("Grade: B")
} else if marks >= 60 {
    print("Grade: C")
} else {
    print("Grade: F")
}
// Output: Grade: C

Swift checks each condition from top to bottom. As soon as one condition is true, it runs that block and skips the rest.

Nested if Statements

let hasID = true
let age = 20

if hasID {
    if age >= 18 {
        print("Entry allowed.")
    } else {
        print("Too young to enter.")
    }
} else {
    print("ID required.")
}

An if can live inside another if. This handles situations where multiple conditions build on each other.

Combining Conditions

let username = "admin"
let password = "secure123"

if username == "admin" && password == "secure123" {
    print("Login successful.")
} else {
    print("Invalid credentials.")
}

Both conditions must be true for the login to succeed. The && operator requires all parts to pass.

Guard Statement – Early Exit

func processAge(_ age: Int) {
    guard age >= 0 else {
        print("Invalid age.")
        return
    }
    print("Age is valid: \(age)")
}

processAge(25)    // Age is valid: 25
processAge(-5)    // Invalid age.

Why Guard Exists

┌──────────────────────────────────────────────┐
│  Without guard:   With guard:                │
│                                              │
│  if valid {       guard valid else {         │
│    do work          return                   │
│    more work      }                          │
│    more...        do work ← less nesting     │
│  }                more work                  │
│                   more...                    │
│                                              │
│  Guard keeps the main logic at top level.    │
└──────────────────────────────────────────────┘

A guard statement checks a condition and exits early if it fails. It keeps your main logic clean by removing invalid cases upfront.