Go Language: return Error from a function

Go functions return multiple values. Using this feature, most of the Go functions return error value as the last value returned by the function.

For example, below function calculate sum of two integers a and b and a nil, if the numbers are >= 0, else return 0 and an error message.

func add(a int, b int) (int, error) {

         if a < 0 || b < 0 {

                  return 0, fmt.Errorf("sum pf negative numbers is not supported")

         }

         return a + b, nil

}

‘nil’ is like null in other programming languages like Java.

App.go

package main

import "fmt"

func main() {
 result1, err1 := add(10, 20)

 if err1 != nil {
  fmt.Println(err1)
 } else {
  fmt.Println("Sum of 10 and 20 is : ", result1)
 }

 result2, err2 := add(0, -1)

 if err2 != nil {
  fmt.Println(err2)
 } else {
  fmt.Println("Sum of 0 and -1 is : ", result2)
 }
}

func add(a int, b int) (int, error) {
 if a < 0 || b < 0 {
  return 0, fmt.Errorf("sum pf negative numbers is not supported")
 }

 return a + b, nil
}

Output

Sum of 10 and 20 is :  30

sum pf negative numbers is not supported

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Go Language: Functions continued

When two or more consecutive parameters to a function taking same type, you can omit the type from all except the last.

func add(x, y, z int) int {

         return x + y + z

}

App.go

package main

import (
 "fmt"
)

func main() {
 result := add(10, 20, 30)

 fmt.Println("Sum of 10, 20, 30 is ", result)

}

func add(x, y, z int) int {
 return x + y + z
}

Output

Sum of 10, 20, 30 is  60

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Go language: Return a value from function

Functions in Go can be written zero or more values.

Syntax

func functionName(parameters) returnType{

         statements

        

         return value

}

You can return a value from a function using ‘return’ keyword.

func add(a int, b int) int{

         return a + b

}

HelloWorld.go

package main

import "fmt"

func main() {

 result := add(10, 20)

 fmt.Println("Sum of 10 and 20 is : ", result)

}

func add(a int, b int) int{
 return a + b
}

Output

Sum of 10 and 20 is :  30

Returning multiple values from a function

You can return multiple values from a function­­.

Syntax

func functionName(parameters) (returnType1, … returnType N){

         statements

        

         return value1, … valueN

}

Example

func arithmetic(a int, b int) (int, int, int, int){

         return a + b, a - b, a *b, a / b

}

HelloWorld.go

package main

import "fmt"

func main() {

 addition, subtraction, multiplication, division := arithmetic(10, 20)

 fmt.Println("Sum of 10 and 20 is : ", addition)
 fmt.Println("Subtraction of 10 and 20 is : ", subtraction)
 fmt.Println("Multiplication of 10 and 20 is : ", multiplication)
 fmt.Println("Division of 10 and 20 is : ", division)

}

func arithmetic(a int, b int) (int, int, int, int){
 return a + b, a - b, a *b, a / b
}

Output

Sum of 10 and 20 is :  30

Subtraction of 10 and 20 is :  -10

Multiplication of 10 and 20 is :  200

Division of 10 and 20 is :  0

Named parameters

Just add the names to the return types in function signature.

Example

func arithmetic(a int, b int) (sum int, sub int, mul int, div int){

         sum =  a + b

         sub = a - b

         mul = a *b

         div = a / b

         return

}

HelloWorld.go

package main

import "fmt"

func main() {

 addition, subtraction, multiplication, division := arithmetic(10, 20)

 fmt.Println("Sum of 10 and 20 is : ", addition)
 fmt.Println("Subtraction of 10 and 20 is : ", subtraction)
 fmt.Println("Multiplication of 10 and 20 is : ", multiplication)
 fmt.Println("Division of 10 and 20 is : ", division)

}

func arithmetic(a int, b int) (sum int, sub int, mul int, div int){
 sum =  a + b
 sub = a - b
 mul = a *b
 div = a / b

 return
}

Output

Sum of 10 and 20 is :  30

Subtraction of 10 and 20 is :  -10

Multiplication of 10 and 20 is :  200

Division of 10 and 20 is :  0

A return statement without arguments returns the named return values. This is known as a "naked" return.

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