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Huseyn
Huseyn

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Variadic Function in Go

#go #backend

What is a Variadic Function in Go?
A variadic function is a function that accepts a variable number of arguments of the same type.

This is useful when you don’t know how many values a caller might pass. Instead of defining a fixed number of parameters, you allow the caller to pass zero or more arguments.

Syntax

func myFunc(args ...int) {
    // args is a slice of int
}
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  • The ... before the type means the function accepts any number of int arguments, including none.
  • Inside the function, args behaves like a slice ([]int).

Real-World Example: Sum of Prices
Imagine you’re summing prices of products in a cart:

package main

import "fmt"

// Variadic function to sum prices
func SumPrices(prices ...float64) float64 {
    total := 0.0
    for _, price := range prices {
        total += price
    }
    return total
}

func main() {
    fmt.Println(SumPrices(10.99, 20.00))                  // 30.99
    fmt.Println(SumPrices(5.99, 15.50, 9.99, 1.99))        // 33.47
    fmt.Println(SumPrices())                              // 0.0
}
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Key Points

Feature Explanation
...type Used only in the last parameter of the function.
Internally Treated as a slice (e.g., []int, []string).
Optional Can pass zero or more values.
Expand slice Use myFunc(mySlice...) to expand a slice into arguments.

Gotchas

func printNames(names ...string) {
    for _, name := range names {
        fmt.Println(name)
    }
}

func main() {
    myNames := []string{"Alice", "Bob", "Carol"}

    // You must use ... to expand a slice
    printNames(myNames...) // ✅
    // printNames(myNames) // ❌ compile error
}
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When to Use Variadic Functions

  • Calculations (sum, average)
  • Logging utilities
  • Formatting strings
  • Joining or filtering collections

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