Go if else

In computer programming, we use the if statement to run a block code only when a certain condition is met.

For example, assigning grades (A, B, C) based on marks obtained by a student.

• if the percentage is above 90, assign grade A
• if the percentage is above 75, assign grade B
• if the percentage is above 65, assign grade C

Go if statement

The syntax of the if statement in Go programming is:

if test_condition {
   // code
}

If test_condition evaluates to

• true - statements inside the body of if are executed.
• false - statements inside the body of if are not executed.

Example: Simple if statement in Golang

// Program to display a number if it is positive

package main
import "fmt"

func main() {
  number := 15

  // true if number is less than 0
  if number > 0 {
    fmt.Printf("%d is a positive number\n", number)
  }

  fmt.Println("Out of the loop")
}

Output

15 is a positive number
Out of the loop

In the above example, we have created a variable named number. Notice the condition,

number > 0

Here, since the variable number is greater than 0, the condition evaluates true.

If we change the variable to a negative integer. Let's say -5.

number := -5

Now, when we run the program, the output will be:

Out of the loop

This is because the value of number is less than 0. Hence, the condition evaluates to false. And, the body of the if block is skipped.

Go if...else statement

The if statement may have an optional else block. The syntax of the if..else statement is:

if test_condition {
    // run code if test_condition is true
} else {
    // run code if test_condition is false
}

If test_condition evaluates to true,

• the code inside if is executed
• the code inside else is skipped

If test_condition evaluates to false,

• the code inside else is executed
• the code inside if is skipped

Example: if...else statement in Golang

package main
import "fmt"

func main() {
  number := 10

  // checks if number is greater than 0
  if number > 0 {
    fmt.Printf("%d is a positive number\n", number)
  } else {
    fmt.Printf("%d is a negative number\n", number)
  }
}

Output

10 is a positive number

The number is 10, so the test condition number > 0 is evaluated to be true. Hence, the statement inside the body of if is executed.

If we change the variable to a negative integer. Let's say -5.

number := -5

Now if we run the program, the output will be:

-5 is a negative number

Here, the test condition evaluates to false. Hence code inside the body of else is executed.

Note: The else statement must start in the same line where the if statement ends.

Go if...else if ladder

The if...else statement is used to execute a block of code among two alternatives.

However, if you need to make a choice between more than two alternatives, then we use the else if statement.

if test_condition1 {
   // code block 1
} else if test_condition2 {
   // code block 2
}.
.
.
} else {
   // code block 3
}

Here,

if test_condition1 evaluates to true

• code block 1 is executed
• code block 2 and code block 3 are skipped

if test_condition2 evaluates to true

• code block 2 is executed
• code block 1 and code block 3 are skipped

if both test conditions evaluates to false

• code block 3 is executed
• code block 1 and code block 2 are skipped

Example: if...if else ladder statement in Golang

// Program to relate two integers using =, > or < symbol

package main
import "fmt"

func main() {

  number1 := 12
  number2 := 20

  if number1 == number2 {
    fmt.Printf("Result: %d == %d", number1, number2)
  } else if number1 > number2 {
    fmt.Printf("Result: %d > %d", number1, number2)
  } else {
    fmt.Printf("Result: %d < %d", number1, number2)     
  }
}

Output

Result: 12 < 20

Here, both the test conditions number1 == number2 and number1 > number2 are false. Hence the code inside the else block is executed.

Go nested if statement

You can also use an if statement inside of an if statement. This is known as a nested if statement.

// outer if statement
if test_condition1 {
  // statements

  // inner if...else statement
  if test_condition2 {
    // statements
  }else {
    // statements
  }
}

Example: Nested if statement in Golang

package main
import "fmt"

func main() {

  number1 := 12
  number2 := 20

  // outer if statement
  if number1 >= number2 {

  // inner if statement
  if number1 == number2 {
    fmt.Printf("Result: %d == %d", number1, number2)
    // inner else statement
  } else {
    fmt.Printf("Result: %d > %d", number1, number2)
  } 

  // outer else statement
  } else {
    fmt.Printf("Result: %d < %d", number1, number2)
  }
}

Output

Result: 12 < 20

If the outer condition number1 >= number2 is true

• inner if condition number1 == number2 is checked
• if condition is true, code inside the inner if is executed
• if condition is false, code inside the inner else is executed

If the outer condition is false, the outer else statement is executed.