Slice creation in Go - Mini Project: Build & Apply

Slice creation

📖 Scenario: You are organizing a small fruit basket for a friend. You want to keep track of the fruits you have using a list-like structure called a slice in Go.

🎯 Goal: Create a slice of fruits, add a few fruit names, and then display the list.

📋 What You'll Learn

Create a slice of strings called fruits with the exact fruits: "Apple", "Banana", "Cherry"

Create a variable called extraFruit and set it to "Mango"

Add extraFruit to the fruits slice using the append function

Print the fruits slice to show all fruits

💡 Why This Matters

🌍 Real World

Slices are used in Go to store lists of items like names, numbers, or objects. This is common in apps that manage collections such as shopping lists, user data, or inventory.

💼 Career

Understanding slices is essential for Go programming jobs because they are a fundamental way to handle groups of data efficiently.

1

Create the initial slice of fruits

Create a slice of strings called fruits with these exact values: "Apple", "Banana", "Cherry"

Go

package main

import "fmt"

func main() {
    // Create the slice fruits here
    // Your code here
}

Hint

Use fruits := []string{} to create a slice with the fruit names inside curly braces.

2

Add an extra fruit variable

Create a variable called extraFruit and set it to the string "Mango"

Go

package main

import "fmt"

func main() {
    fruits := []string{"Apple", "Banana", "Cherry"}
    // Create extraFruit variable here
    // Your code here
}

Hint

Use extraFruit := "Mango" to create the variable.

3

Add the extra fruit to the slice

Use the append function to add extraFruit to the fruits slice and update fruits with the result

Go

package main

import "fmt"

func main() {
    fruits := []string{"Apple", "Banana", "Cherry"}
    extraFruit := "Mango"
    // Append extraFruit to fruits slice
    // Your code here
}

Hint

Use fruits = append(fruits, extraFruit) to add the new fruit.

4

Print the fruits slice

Write a fmt.Println statement to print the fruits slice

Go

package main

import "fmt"

func main() {
    fruits := []string{"Apple", "Banana", "Cherry"}
    extraFruit := "Mango"
    fruits = append(fruits, extraFruit)
    // Print the fruits slice
    // Your code here
}

Hint

Use fmt.Println(fruits) to display the slice contents.

Practice

1. What is a slice in Go programming?

easy

A. A flexible, dynamically-sized list of elements.

B. A fixed-size array that cannot change length.

C. A function that slices strings.

D. A type of map with keys and values.

Solution

1. Step 1: Understand slice definition

   A slice in Go is a data structure that holds a list of elements and can grow or shrink in size.

2. Step 2: Compare with other types

   Unlike arrays, slices are dynamic and flexible, unlike maps or functions.

3. Final Answer:

   A flexible, dynamically-sized list of elements. -> Option A

4. Quick Check:

   Slice = dynamic list [OK]

Hint: Remember: slices can grow, arrays cannot [OK]

Common Mistakes:

• Confusing slices with fixed-size arrays
• Thinking slices are functions
• Mixing slices with maps

2. Which of the following is the correct way to create an empty slice of integers in Go?

easy

A. var s []int

B. s := []int{}

C. s := make([]int, 0)

D. All of the above

Solution

1. Step 1: Review slice creation methods

   In Go, you can create an empty slice by declaring a nil slice, using a slice literal with no elements, or using make with length zero.

2. Step 2: Confirm all options are valid

   All three options create an empty slice of integers correctly.

3. Final Answer:

   All of the above -> Option D

4. Quick Check:

   Empty slice creation = D [OK]

Hint: Empty slices can be made in multiple valid ways [OK]

Common Mistakes:

• Using make with negative length
• Confusing array and slice syntax
• Forgetting to initialize slice before use

3. What will be the output of this Go code?

package main
import "fmt"
func main() {
  s := []int{1, 2, 3}
  s = append(s, 4)
  fmt.Println(s)
}

medium

A. [1 2 3]

B. [1 2 3 4]

C. [4]

D. Compilation error

Solution

1. Step 1: Understand initial slice and append

   The slice s starts with elements 1, 2, 3. The append function adds 4 to the end.

2. Step 2: Print the updated slice

   After append, s contains [1 2 3 4], which is printed.

3. Final Answer:

   [1 2 3 4] -> Option B

4. Quick Check:

   append adds element to slice [OK]

Hint: append adds elements to the end of a slice [OK]

Common Mistakes:

• Expecting append to replace elements
• Thinking append returns a new slice without assignment
• Confusing slice with array syntax

4. Identify the error in this Go code snippet:

package main
func main() {
  s := make([]int, 3)
  s[3] = 10
}

medium

A. Slice s is nil

B. Syntax error in make function

C. Index out of range error at s[3]

D. No error, code runs fine

Solution

1. Step 1: Analyze slice length and indexing

   make([]int, 3) creates a slice with length 3, valid indices are 0, 1, 2.

2. Step 2: Check index used in assignment

   Accessing s[3] is out of range and causes a runtime panic.

3. Final Answer:

   Index out of range error at s[3] -> Option C

4. Quick Check:

   Slice indices start at 0, max index = length-1 [OK]

Hint: Slice indices go from 0 to length-1 only [OK]

Common Mistakes:

• Using index equal to slice length
• Confusing slice length and capacity
• Assuming make creates larger slice than specified

5. Given the code below, what will be the length and capacity of slice s after execution?

package main
import "fmt"
func main() {
  s := make([]int, 2, 5)
  s = append(s, 3, 4, 5)
  fmt.Println(len(s), cap(s))
}

hard

A. 5 5

B. 5 10

C. 7 10

D. 3 5

Solution

1. Step 1: Understand make parameters

   make([]int, 2, 5) creates a slice with length 2 and capacity 5.

2. Step 2: Append three elements

   Appending 3 elements increases length from 2 to 5, capacity remains 5 as it is enough.

3. Final Answer:

   5 5 -> Option A

4. Quick Check:

   Length grows with append, capacity stays if enough [OK]

Hint: Capacity grows only if append exceeds current capacity [OK]

Common Mistakes:

• Assuming capacity doubles automatically
• Confusing length and capacity
• Forgetting append increases length