【Go自学】一文搞懂Go append方法

我们先看一下append的源码

// The append built-in function appends elements to the end of a slice. If
// it has sufficient capacity, the destination is resliced to accommodate the
// new elements. If it does not, a new underlying array will be allocated.
// Append returns the updated slice. It is therefore necessary to store the
// result of append, often in the variable holding the slice itself:
//
//	slice = append(slice, elem1, elem2)
//	slice = append(slice, anotherSlice...)
//
// As a special case, it is legal to append a string to a byte slice, like this:
//
//	slice = append([]byte("hello "), "world"...)
func append(slice []Type, elems ...Type) []Type

 源码中定义了三种apped的使用场景：

1、为切片添加同种类型的元素

slice = append(slice, elem1, elem2)

2、将两个切片拼接到一起

slice = append(slice, anotherSlice...)

3、当切片是byte类型时，允许添加string类型的元素

slice = append([]byte("hello "), "world"...)

一、append()追加元素 

package mainimport "fmt"func main() {a := make([]int, 5, 10)for i := 0; i < len(a); i++ {a[i] = i}fmt.Println(a)a = append(a, 5,6, 7, 8, 9, 10)fmt.Println(a)
}

输出结果

[0 1 2 3 4]
[0 1 2 3 4 6 7 8 9 10]

 二、append()追加切片

package mainimport "fmt"func main() {a := make([]int, 5, 10)for i := 0; i < len(a); i++ {a[i] = i}fmt.Println(a)b := make([]int, 5, 10)for i := 5; i < len(b)+5; i++ {b[i-5] = i}fmt.Println(b)a = append(a, b...)fmt.Println(a)
}

 输出结果

[0 1 2 3 4]
[5 6 7 8 9]
[0 1 2 3 4 5 6 7 8 9]

根据append可以添加切片的性质，使用append可以实现删除一个切片中某一个元素或删除某一段连续元素的功能。

package mainimport "fmt"func main() {a := make([]int, 5, 10)for i := 0; i < len(a); i++ {a[i] = i}fmt.Println(a)a = append(a[:2], a[4:]...) //删除a[2],a[3]fmt.Println(a)
}

输出结果

[0 1 2 3 4]
[0 1 4]

三、向[]byte切片中添加string元素

package mainimport "fmt"func main() {a := []byte("Hello")fmt.Println(a, string(a))a = append(a, "World"...)fmt.Println(a, string(a))
}

输出结果

[72 101 108 108 111] Hello
[72 101 108 108 111 87 111 114 108 100] HelloWorld