Go – Convert Array to Slice

In Go, arrays and slices are closely related data structures. While arrays have a fixed size, slices are dynamic and can grow or shrink. You can easily convert an array into a slice, enabling you to leverage the dynamic features of slices while working with the data stored in arrays.

In this tutorial, we will explore how to convert arrays into slices using simple syntax, along with practical examples and detailed explanations.

Syntax for Converting Array to Slice

The syntax to convert an array to a slice is straightforward:

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slice := array[start:end]

Here:

  • array: The array to be converted.
  • start: The starting index (inclusive).
  • end: The ending index (exclusive).

If you omit start or end, the slice includes all elements from the beginning or until the end of the array, respectively.

Examples of Converting Array to Slice

1. Convert Entire Array to Slice

Here’s how to convert an entire array into a slice:

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package main

import "fmt"

func main() {
    // Declare and initialize an array
    var arr = [5]int{10, 20, 30, 40, 50}

    // Convert the entire array to a slice
    slice := arr[:]

    // Print the slice
    fmt.Println("Slice:", slice)
}

Explanation

  1. Declare Array: The array arr is declared and initialized with 5 elements.
  2. Convert to Slice: The entire array is converted into a slice using the slice expression arr[:].
  3. Print Slice: The resulting slice is printed using fmt.Println.

Output

2. Convert Partial Array to Slice

Here’s how to convert a portion of an array into a slice:

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package main

import "fmt"

func main() {
    // Declare and initialize an array
    var arr = [5]int{10, 20, 30, 40, 50}

    // Convert part of the array to a slice
    slice := arr[1:4]

    // Print the slice
    fmt.Println("Slice:", slice)
}

Explanation

  1. Declare Array: The array arr is declared and initialized with 5 elements.
  2. Convert to Slice: A portion of the array (from index 1 to index 3) is converted into a slice using arr[1:4].
  3. Print Slice: The resulting slice is printed using fmt.Println.

Output

3. Convert Array to Slice and Modify Elements

When you convert an array to a slice, changes to the slice affect the original array:

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package main

import "fmt"

func main() {
    // Declare and initialize an array
    var arr = [5]int{10, 20, 30, 40, 50}

    // Convert the array to a slice
    slice := arr[:]

    // Modify an element in the slice
    slice[2] = 99

    // Print the updated slice and array
    fmt.Println("Slice:", slice)
    fmt.Println("Array:", arr)
}

Explanation

  1. Convert to Slice: The entire array is converted into a slice using arr[:].
  2. Modify Slice: An element in the slice is updated using its index.
  3. Reflect Changes: The changes to the slice are reflected in the original array since slices share the underlying array memory.

Output

Points to Remember

  • Shared Memory: Slices share the same underlying memory as the array. Modifications to the slice will affect the original array.
  • Partial Conversion: You can convert a portion of an array into a slice using the slice expression [start:end].
  • Dynamic Nature: Once converted, slices can be resized dynamically using functions like append.
  • Default Behavior: Omitting start or end in the slice expression includes all elements from the start or until the end, respectively.