Conditionals

Syntax

if condition {
    // ...
} else if otherCondition {
    // ...
} else {
    // ...
}

• No parentheses around the condition.
• Braces are always required, even for a single line.
• else must be on the same line as the closing }.

An if can also start with a short init statement, separated from the condition by ;. Variables declared there only exist inside the if/else blocks:

if n, err := strconv.Atoi(input); err != nil {
    fmt.Println("not a number")
} else {
    fmt.Println("you typed", n)
}
// n and err don't exist here

Example

package main

import (
    "fmt"
    "strconv"
)

func main() {
    temperature := 28

    if temperature > 30 {
        fmt.Println("Hot")
    } else if temperature > 20 {
        fmt.Println("Warm")
    } else {
        fmt.Println("Cold")
    }

    if n, err := strconv.Atoi("42"); err == nil {
        fmt.Println("Parsed:", n)
    }

    loggedIn := true
    isAdmin := false
    if loggedIn && !isAdmin {
        fmt.Println("Regular user")
    }
}

Expected output

Warm
Parsed: 42
Regular user

Common mistakes

• Using a non-boolean as a condition. Go has no "truthy" values, so if count { ... } fails with non-boolean condition in if statement — write if count != 0.
• Putting else on a new line after } — a syntax error because of automatic semicolon insertion.
• Trying to use a variable from an if init statement after the if has ended.

Practice

Given score := 73, print Pass if the score is 50 or more and Fail otherwise. Then, using an init statement, parse the string "19" and print Adult if it's 18 or more.

package main

import (
    "fmt"
    "strconv"
)

func main() {
    score := 73
    if score >= 50 {
        fmt.Println("Pass")
    } else {
        fmt.Println("Fail")
    }

    if age, err := strconv.Atoi("19"); err == nil && age >= 18 {
        fmt.Println("Adult")
    }
}