How to Pass a Slice of Slices as Unpacked Arguments to a Variadic Function in Go?

Unpacking Slice of Slices as Variadic Arguments

Problem:
When attempting to pass a slice of slices as unpacked arguments to a variadic function, a compilation error occurs. The error indicates an inability to assign the source slice type to the destination variadic parameter type.

Explanation:
According to the Go specification, a function with variadic parameters of type ...T expects a single slice of type []T as an argument. However, in the case of a slice of slices, [][]T, this condition cannot be met.

Solution:
To resolve this issue, a new slice of the required type []T must be created and populated with the desired values. This new slice can then be passed unpacked using the ellipsis operator (...).

Example:

<code class="go">package main

import (
    "fmt"
)

func unpack(args ...interface{}) {
    fmt.Println(len(args))
}

func main() {
    sliceOfSlices := [][]int{
        []int{1, 2},
        []int{101, 102},
    }

    // Create a new slice of type []interface{}
    sliceOfInterfaces := []interface{}{}
    for _, v := range sliceOfSlices {
        sliceOfInterfaces = append(sliceOfInterfaces, v)
    }

    unpack(sliceOfInterfaces...) // Pass unpacked values
}</code>

Output:

2

In this example, the unpack() function is called with the unpacked elements of the sliceOfSlices as arguments. The len() function is used to demonstrate the number of arguments passed, which indicates that both elements of the nested slice are unpacked.

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