This is the chapter 12 of the golang comprehensive tutorial series. Refer to this link for other chapters of the series – Golang Comprehensive Tutorial Series

Next Tutorial – Switch
Previous Tutorial – For Range loop

Now let’s check out the current tutorial. Below is the table of contents for current tutorial.

Overview

Go has if-else statement similar to any other programming language to perform the basic conditional logic. Below is the format for if-else statement in golang

if condition {
   //Do something
} else if condition {
   //Do something
} else {
   //Do something

Before we move further let’s talk about the condition first. Only a statement or a combination of statements that result in a boolean are allowed for a condition in if. false boolean is treated as false in a condition in go and true boolean is treated as true. As mentioned above, the condition can be composed of multiple statements combined by operators in Go such as &&, ||, >, <, >=, <=, ! etc.

Now let’s look into the if-else statement in detail to understand the small things. Go supports below formats for the if-else statement

Only if
If Else
If Else Ladder
Nested if-else
If with a short statement

If statement

if statement alone has below format

if condition {
   //Do something
}

If the condition is true then the statement inside the braces is executed. Some points to note about if statement

Brackets can be omitted around the condition.

Opening and closing braces after condition are mandatory

Let’s see a working example. Below program checks if a number is greater than 5.

package main

import "fmt"

func main() {
    a := 6
    if a > 5 {
        fmt.Println("a is greater than 5")
    }
}

Output

a is greater than 5

Let’s see another example of multiple statement in a if condition. Below is a program to check if a number lies in a particular range. Notice that multiple statement in the condition are joined by the && operator.

package main

import "fmt"

func main() {
    a := 4
    if a > 3 && a < 6 {
        fmt.Println("a is within range")
    }
}

Output

a is within range

If Else Statement

If Else statement has below format

if condition {
   //Do something
} else {
   //Do something
}

If the condition is true then the statement inside the if block is executed otherwise the statement inside the else block is executed. Some points to note about if-else statement.

The else keyword should be on the same line as the closing brace for it. If not there will be below compiler error.

syntax error: unexpected else, expecting }

Let's see a small example of if else statement. In below program we use if else statement to figure out the max number of 2 numbers

package main

import "fmt"

func main() {
    a := 1
    b := 2

    if a > b {
        fmt.Println("a is greater than b")
    } else {
        fmt.Println("b is greater than a")
    }
}

Output

b is greater than a

If Else Ladder

If Else ladder has the below format

if condition1 {
   //Do something
} else if condition2 {
   //Do something
} else {
  //Do something
}

Some points to note about this if else ladder

Any number of else if statement can be added in the middle

else if should lie on the same line as the previous closing brace

Below is a working code example. The code given an age is using a if else ladder to find out weather a person is "Kid", "Young" or "Old".

package main

import "fmt"

func main() {
    age := 29
    if age < 18 {
        fmt.Println("Kid")
    } else if age >= 18 && age < 40 {
        fmt.Println("Young")
    } else {
        fmt.Println("Old")
    }
}

Output:

Young

Nested If Else

Below are some one of the possible format for nested if else.

Only nested if

if condition {
  //Do something
  if condition2 { 
    //Do something
  }
  //Do something
}

Nested if else

if condition1 {
   //....
   if condition2 {
      //...
   } else {
      //...
   }
  //...
}

Below combination is also possible for nested if else

if condition1 {
   //...
} else {
   //...
   if condition2 {
      //...
   } else {
     //....
   }
   //....
}

Let's see a working example of nested if else. In below program we print the max of three numbers using nested if else.

package main

import "fmt"

func main() {
    a := 1
    b := 2
    c := 3
    if a > b {
        if a > c {
            fmt.Println("Biggest is a")
        } else if b > c {
            fmt.Println("Biggest is b")
        }
    } else if b > c {
        fmt.Println("Biggest is b")
    } else {
        fmt.Println("Biggest is c")
    }
}

Output:

Biggest is c

If with short statement

If statement also supports a statement before the condition. This statement will be executed before the condition. There can also be new initialized variable in the statement. Below is the format for that.

if statement; condition {
   //Do something
}

The initialization if present in the statement will be a short declaration. Notice that var keyword is not supported in the statement. Let's see a working example

package main

import "fmt"

func main() {
    if a := 6; a > 5 {
        fmt.Println("a is greater than 5")
    }
}

Output

a is greater than 5

The variable that is initialized in if statement is available inside all the branches. As in below example variable a is also available in the else block.

package main

import "fmt"

func main() {
    if a := 1; a > 5 {
        fmt.Println("a is greater than 5")
    } else {
        fmt.Println("a is less than 5")
    }
}

Output:

a is less than 5

If Conditions

We mentioned at the start that only boolean values or statement that result in boolean value are allowed in the if condition. Let's see a working code of the error that comes in case of using any else than boolean

package main

import "fmt"

func main() {
    if 1 {
        fmt.Println("a is greater than 5")
    }
}

Output: Below compiler error is raised

non-bool 1 (type int) used as if condition

Ternary Operator

There is no ternary operator in Go, hence you need to use if else statements in place of that.

Conclusion

That is all about if else statement in go. Hope you have liked this article. Please share feedback/improvements/mistakes in comments

Next Tutorial – Switch
Previous Tutorial – For Range loop

complete

golang

guide

understand

using