Go Slice Clear

In Go, clearing a slice means removing all its elements or resetting its length to zero. While Go does not have a built-in method like clear() in some other languages, you can achieve this by re-slicing or assigning a new slice. Clearing a slice does not affect its underlying array unless explicitly handled.

In this tutorial, we will explore how to clear a slice in Go using various methods with examples and detailed explanations.

Methods to Clear a Slice

  • Re-slicing: Set the slice length to zero while retaining the underlying array.
  • Assigning a New Slice: Assign an empty slice to the variable, effectively replacing the original slice.
  • Clearing Underlying Data: Explicitly set all elements in the underlying array to their default values.

Examples of Clearing a Slice

1. Clear a Slice Using Re-Slicing

This example demonstrates how to clear a slice by re-slicing it to zero length:

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package main

import "fmt"

func main() {
    // Initialize a slice
    numbers := []int{10, 20, 30, 40, 50}

    // Clear the slice by re-slicing
    numbers = numbers[:0]

    // Print the result
    fmt.Println("Cleared Slice:", numbers)
    fmt.Println("Length:", len(numbers))
    fmt.Println("Capacity:", cap(numbers))
}

Explanation

  1. Initialize Slice: A slice named numbers is initialized with five elements.
  2. Re-slicing: The slice is re-sliced using numbers[:0], setting its length to zero while retaining its capacity and underlying array.
  3. Print Results: The cleared slice is printed, showing an empty slice with a length of 0 but the same capacity as the original slice.

Output

2. Clear a Slice by Assigning a New Slice

This example demonstrates how to clear a slice by assigning a new, empty slice:

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package main

import "fmt"

func main() {
    // Initialize a slice
    numbers := []int{10, 20, 30, 40, 50}

    // Clear the slice by assigning a new slice
    numbers = []int{}

    // Print the result
    fmt.Println("Cleared Slice:", numbers)
    fmt.Println("Length:", len(numbers))
    fmt.Println("Capacity:", cap(numbers))
}

Explanation

  1. Initialize Slice: A slice named numbers is initialized with five elements.
  2. Assign a New Slice: A new empty slice ([]int{}) is assigned to the numbers variable, effectively clearing it.
  3. Print Results: The cleared slice is printed, showing an empty slice with both length and capacity set to 0.

Output

3. Clear the Underlying Data

This example demonstrates how to clear a slice by resetting all elements in the underlying array:

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package main

import "fmt"

func main() {
    // Initialize a slice
    numbers := []int{10, 20, 30, 40, 50}

    // Clear the underlying data
    for i := range numbers {
        numbers[i] = 0
    }

    // Print the result
    fmt.Println("Cleared Slice:", numbers)
}

Explanation

  1. Initialize Slice: A slice named numbers is initialized with five elements.
  2. Reset Elements: A for loop iterates through the slice, setting each element to its default value (0 for integers).
  3. Print Results: The cleared slice is printed, showing all elements set to 0.

Output

Points to Remember

  • Re-Slicing: Setting the length to zero retains the slice’s capacity and underlying array.
  • New Slice: Assigning a new slice resets both length and capacity to zero, releasing the reference to the original array.
  • Underlying Data: Resetting the underlying array explicitly clears the data but retains the slice’s length and capacity.
  • Memory Management: Be mindful of memory usage when clearing slices, especially if they retain references to large arrays.