Let’s talk about how to use Golang’s slicing and append() functions

In Golang's slice, append() is a very important function and a very frequently used function. This article will introduce how to use Golang's slicing and append() functions.

1. Golang slicing

Compared with arrays, slicing has more powerful functions in Golang. A slice differs from an array in that its length can change dynamically. In Golang, a slice is a reference type that points to an underlying array. When the slice capacity is insufficient, the slice size will be automatically increased as needed.

The way to define a slice is as follows:

var s1 []int // []int 表示定义了一个 int 类型的切片

The length and capacity of s1 at this time are both 0 because the underlying array is not defined.

Defining a slice with a length of 5 and a capacity of 10 can be implemented using the make() function:

s2 := make([]int, 5, 10) // 长度为 5，容量为 10

slice[index] can access the elements in the slice, which are essentially elements in the underlying array . slice[start:end] can get sub-slices from start (inclusive) to end (exclusive). For example:

a := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
fmt.Println(a[3])    // 4
fmt.Println(a[1:5])  // [2 3 4 5]
fmt.Println(a[:5])   // [1 2 3 4 5]
fmt.Println(a[5:])   // [6 7 8 9 10]
fmt.Println(a[:])    // [1 2 3 4 5 6 7 8 9 10]

2. append() function

append() function can add elements to the end of the slice and return a new slice. The append() function has the following uses.

1. Add elements to the end of the slice

The following code adds elements to s1 and generates a new slice:

s1 := []int{1, 2, 3, 4, 5}
s2 := append(s1, 6, 7)
fmt.Println(s1) // [1 2 3 4 5]
fmt.Println(s2) // [1 2 3 4 5 6 7]

Note: Use the append() function When adding elements to a slice, the underlying array is not changed if the capacity is not exceeded, and a new underlying array is generated if the capacity is exceeded.

2. Add one slice to another slice

The following code adds elements of s2 to s1 and generates a new slice:

s1 := []int{1, 2, 3, 4, 5}
s2 := []int{6, 7}
s3 := append(s1, s2...)
fmt.Println(s1) // [1 2 3 4 5]
fmt.Println(s2) // [6 7]
fmt.Println(s3) // [1 2 3 4 5 6 7]

Note: When using the append() function to add one slice to another slice, you need to add three dots (...) after s2, which means that s2 is split and the elements are taken out.

3. Generate a new slice through append()

The following code creates a slice s1 with a length of 0 and a capacity of 0, and then adds elements to it:

var s1 []int
s1 = append(s1, 1)
s1 = append(s1, 2, 3)
fmt.Println(s1) // [1 2 3]

The append() function will return the newly generated slice. If the original slice length is not enough, a new array will be created, so the append() function can be used when the slice length is 0.

3. Summary

Through the introduction of this article, we have learned about the usage of Golang slicing and append() functions. Slicing is very important in Golang and is used very frequently in actual development. It is very important for Golang developers to master the basic usage of slicing. When using the append() function, you need to pay attention to its return value, and you need to pay special attention to using the ... operator to split one slice and add it to another slice.

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