Condition Selection in Go with Examples

Condition selection is a mechanism to execute certain code based on a specified condition. There are many condition selection types in Go including selection with if, selection with if else, selection with if else if and selection with switch case.

Logic Operator

When using condition selection, the logic operator is used. There are two operators that can be used including AND (&&) and OR (||).

OR Operator (||)

This operator returns true if one or two conditions are true.

AND Operator (&&)

This operator returns true if two conditions are true.

Comparation Operator

The comparation operator can be used together with logic operator if needed. This is the list of comparation operators that can be used in Go.

Selection using if

This is the basic syntax of condition selection using if. If the condition is suitable or fulfilled then the code inside if block is executed.

if condition {
    // code..
}

In this example, the condition selection is used to check if a number is an odd number.

package main

import (
    "fmt"
)

func main() {
    var num int32 = 25

    if num%2 != 0 {
        fmt.Println("Odd number")
    }
}

Output

Odd number

Based on the code above, the condition selection using if is used to check if a number is an odd number. Because the result of num % 2 is not equals zero then the condition is fulfilled so the code inside if block is executed.

Selection using if else

This is the basic syntax of condition selection using if else. If the condition is fulfilled then the code inside if block is executed. Otherwise, if the condition is not fulfilled then the code inside else block is executed.

if condition {
    // code..
} else {
    // code..
}

In this example, the condition using if else is used to check if an username is a valid username.

package main

import (
    "fmt"
)

func main() {
    var username string = "firstname"

    // perform validation with if else
    if len(username) >= 6 && username != "" {
        fmt.Println("Welcome, ", username)
    } else {
        fmt.Println("Username is invalid")
    }
}

Output

Welcome,  firstname

Based on the code above, the if else condition selection is used to check if an username is valid username. The valid condition is if the length of username is greater than or equals 6 and the username is not empty. Because the condition is fulfilled then the code inside if block is executed.

If the condition is not fulfilled, the code inside else block is executed.

package main

import (
    "fmt"
)

func main() {
    var username string = "hi"

    // perform validation with if else
    if len(username) >= 6 && username != "" {
        fmt.Println("Welcome, ", username)
    } else {
        fmt.Println("Username is invalid")
    }
}

Output

Username is invalid

Selection using if else if

This is the basic syntax of condition selection using if else if.

if condition {
    // code..
} else if condition {
    // code..
} else {
    // code..
}

In this example, the if else if condition selection is used to define a grade in alphabet. The grade criteria is defined in this table.

package main

import (
    "fmt"
)

func main() {
    var score int = 78

    if score >= 80 && score <= 100 {
        fmt.Println("A")
    } else if score >= 71 && score <= 79 {
        fmt.Println("B")
    } else if score >= 51 && score <= 70 {
        fmt.Println("C")
    } else if score <= 50 {
        fmt.Println("D")
    } else {
        fmt.Println("Invalid score!")
    }
}

Output

B

Based on the code above, the code is executed based on the condition that fulfilled.

Selection using switch case

This is the basic syntax of condition selection with switch case. The code is executed based on a fulfilled condition in case. If all the conditions in case is not fulfilled then the code inside default is executed.

switch expression {
    case condition:
        // code..
    ..
    default:
        // code..
}

In this example, the condition selection with switch case is used.

package main

import "fmt"

func main() {
    var job string = "Back End Developer"

    switch job {
    case "Front End Developer":
        fmt.Println("Focus on UI and UX")
    case "Back End Developer":
        fmt.Println("Focus on logic")
    case "Mobile Apps Developer":
        fmt.Println("Focus on mobile app development")
    default:
        fmt.Println("Just do it!")
    }
}

Output

Focus on logic

Nested Condition Selection

The nested condition selection is also available in Go. In this example, the nested condition selection is used with if selection.

package main

import "fmt"

func main() {
    var username string = "admin"
    var password string = "secret"

    if username == "admin" {
        if password == "secret" {
            fmt.Println("Welcome admin!")
        } else {
            fmt.Println("Password is invalid!")
        }
    } else {
        fmt.Println("Username is invalid!")
    }

}

Output

Welcome admin!

Based on the code above, the outer condition selection is executed then the inner selection is executed.

Tips to Using Selection

• Use if selections including if, if else or if else if for complex condition like range condition.

• Use switch case selection for simple condition.

I hope this article is helpful to learn condition selection in Go Programming Language.