Go – Slice Deep Copy

In Go, slices are references to underlying arrays, meaning changes to one slice can affect another slice that shares the same underlying array. To avoid this, you can perform a deep copy, where the data of one slice is copied to a new, independent slice. This ensures modifications to one slice do not affect the other.

In this tutorial, we will explore how to perform a deep copy of slices in Go with practical examples and detailed explanations.

Steps to Perform a Deep Copy

Create a New Slice: Create a new slice with the same length as the original slice.
Copy Elements: Use the copy function or a for loop to copy elements from the original slice to the new slice.
Independent Memory: The new slice will have its own backing array, making it independent of the original slice.

Examples of Deep Copy in Go

1 Deep Copy Using the copy Function

This example demonstrates how to use the built-in copy function to perform a deep copy of a slice:

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Copy

package main

import "fmt"

func main() {
    // Declare and initialize a slice
    original := []int{1, 2, 3, 4, 5}

    // Create a new slice with the same length as the original
    copied := make([]int, len(original))

    // Perform a deep copy
    copy(copied, original)

    // Modify the original slice
    original[0] = 10

    // Print both slices
    fmt.Println("Original Slice:", original)
    fmt.Println("Copied Slice:", copied)
}

Explanation

Declare Original Slice: The slice original is initialized with values {1, 2, 3, 4, 5}.
Create Copied Slice: The slice copied is created using make with the same length as the original slice.
Copy Elements: The copy function is used to copy elements from original to copied.
Modify Original: Modifying the original slice does not affect the copied slice.

Output

2 Deep Copy Using a for Loop

This example demonstrates how to manually copy elements using a for loop:

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Copy

package main

import "fmt"

func main() {
    // Declare and initialize a slice
    original := []string{"apple", "banana", "cherry"}

    // Create a new slice with the same length as the original
    copied := make([]string, len(original))

    // Perform a deep copy using a for loop
    for i, v := range original {
        copied[i] = v
    }

    // Modify the original slice
    original[0] = "grape"

    // Print both slices
    fmt.Println("Original Slice:", original)
    fmt.Println("Copied Slice:", copied)
}

Explanation

Declare Original Slice: The slice original is initialized with values {"apple", "banana", "cherry"}.
Create Copied Slice: The slice copied is created using make with the same length as the original slice.
Use for Loop: A for loop iterates through original and copies each element to copied.
Modify Original: Changes to original do not affect copied.

Output

Points to Remember

Independent Slices: A deep copy creates a new slice with its own backing array, independent of the original slice.
Use copy Function: The copy function is the most efficient way to perform a deep copy in Go.
Use for Loop: A for loop can be used for more control over the copying process.
Memory Management: Ensure the new slice has enough capacity to hold all elements of the original slice.

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Go – Slice Deep Copy