Copy a Slice

Lesson 13 of 21 in Coddy's Slices and Maps in Golang course.

In Go, there are some built-in functions that we can use with slices, and we already used one of them in the last lesson, which is the append function. It allows us to add elements to an existing slice. We call these functions helper functions, and you can add this to the difference between arrays and slices in Go; arrays don't have these functions.

In this lesson, we're going to talk about the copy function, which allows us to copy a slice, and it works like this:

str := []string{"Python", "Golang", "Java", "TypeScript"}
newStr := make([]string, 4)
copy(newStr, str)
fmt.Println(newStr)

This will be the output:

[Python Golang Java TypeScript]

Using the copy function, we copy the elements from the str slice to the newStr slice. The syntax is like this: copy(destination, source).

Now, what if the new slice's capacity is less than the source slice? Let's do an example:

str := []string{"Python", "Golang", "Java", "TypeScript"}
newStr := make([]string, 3)
copy(newStr, str)
fmt.Println(newStr)

If we run this, we'll get:

[Python Golang Java]

Because the new slice's capacity is 3, so there is space for only 3 elements.

Let's do an example in the opposite case:

str := []int{23, 34, 56, 77}
newStr := make([]int, 6)
copy(newStr, str)
fmt.Println(newStr)

Here, the new slice's capacity is bigger than the source slice, so the result will copy the elements, and the rest will be the default value, which in the case of an int is 0:

[23 34 56 77 0 0]

Challenge

Easy

Write a program that takes two slices and merges them into a new slice, then prints it to the screen.

In the given code, we define two integer slices.

Here you will need to use the slice operator along with the copy function.

Refer to the hints if you need more help.

Try it yourself

package main

import (
	"fmt"
)

func main() {
    // two Slices Don't Change This!
	str := []int{1, 2, 3, 4}
	str2 := []int{5, 6, 7, 8}
	// Define New Slice 
 
    // Copy element
 
	// Copy with Slice operator
	 
    // Print the new Slice
	fmt.Println()

}

All lessons in Slices and Maps in Golang

1Introduction

Introduction

4Maps

Maps Copy a Map Add and Delete Elements Check for a Key Recap Challenge #1

2Slices

Slices vs Arrays Add Element to Slice Slicing Slicing Ways Reslicing Slice Capacity Max Capacity Iterate Over a Slice Recap Challenge #1

3Slices Behind the Scene

Slice is an Array Slice with MakeCopy a SliceDelete an Element Recap Challenge #1 Recap Challenge #2