Slice with Make

Lesson 12 of 21 in Coddy's Slices and Maps in Golang course.

In the last lessons, we created slices using slice literals. However, there's another function called make. It allows you to allocate a backing array for a slice with a given length and capacity. The reason for having a function like make is because a slice doesn't have a defined length upfront. So, the make function allows you to create a slice with a specified length.

But don't be mistaken; its length doesn't become fixed. You can still append to it.

The syntax for the make function is as follows:

mySlice = make([]string, 4)

You simply use make, and the first argument ([]string) describes the type of the slice, while the second argument (4) tells make the length that we need for our slice. The second argument also describes the capacity of the backing array. So, the returned slice's length and capacity become equal.

Now, the question is why we need to use the make function to create a slice if we can just use the simple slice literal?

Well, the answer is that in some situations, we need to add new values to a slice, and if it doesn't have enough capacity, it will create a new backing array. This operation is a bit expensive in terms of memory because it requires reallocation. The make function prevents this reallocation by preallocating space in memory.

With make, we can specify both length and capacity with different values like this:

mySlice = make([]string, 4, 6)

In general, the make function can be represented as shown below:

Challenge

Easy

Using the make function, create a slice named coddy with a length of 4 and a capacity of 5.

Add the value "Learn Golang" to index 0.
Add the value "Coddy.tech" to index 3.
Iterate over this slice using the range keyword and print the index and the value to the screen.

Try it yourself

package main

import "fmt"

func main() {
    // Create the coddy slice with make  
    
 	// Add elements at the index 0 and 3


    // Iterate Over the coddy slice



}

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 ArraySlice with MakeCopy a Slice Delete an Element Recap Challenge #1 Recap Challenge #2