Slices

Creating Slices

There are three ways to create slices.

package main

import "fmt"

func main() {
	// First way: Declare directly
	var dataSlice []string

	// Second way: Initialize directly
	dataSlice1 := []string{}

	// Third way: Use make
	dataSlice2 := make([]string, 10)

	fmt.Println(dataSlice, dataSlice1, dataSlice2)
}

You can initialize data directly when creating it.

dataSlice1 := []string{"Jack", "Mike"}

Slicing Slices

arr[beginIndex:endIndex] can slice the slice, including the data of the beginIndex and excluding the data of the endIndex.

data := []int{0,1,2,3,4,5}

fmt.Println(data[2:4])

// Result
// [2 3]

Length and Capacity

Use len() to get the length of the slice and cap() to get the capacity of the slice.

Example

package main

import "fmt"

func main() {
	// Create a slice with a length of 5 and a capacity of 9
	data := make([]int, 5, 9)

	fmt.Println(data, len(data), cap(data))
}

// Result:
// [0 0 0 0 0] 5 9

Appending Data

Use the append() function to append data.

Example

package main

import "fmt"

func main() {
	data := []int{0,1,2}

	// Append one piece of data
	data1 := append(data, 3)

	// Append multiple pieces of data
	data2 := append(data, 4, 5, 6)

	fmt.Println(data)
	fmt.Println(data1)
	fmt.Println(data2)
}

// Result:
// [0 1 2]
// [0 1 2 3]
// [0 1 2 4 5 6]

Cloning Slices

We know that slices are reference types. If you assign a slice to another variable, the data sharing the same memory address is actually shared. If you want to create two slices with the same data, you can use the copy() method.

Example

package main

import "fmt"

func main() {
	data := []int{0,1,2}

	// Create a slice with the same length
	data1 := make([]int, len(data))

	// Copy data to data1
	copy(data1, data)

	// Add data to data1
	data1 = append(data1, 3, 4, 5)

	fmt.Println(data)
	fmt.Println(data1)
	
	// You will find that data has not been changed.
}

// Result:
// [0 1 2]
// [0 1 2 3 4 5]