Go語言中的數(shù)組大概相當與C/C++中的數(shù)組，固定大小，不能夠動態(tài)擴展大小，而切片大概相當與C++中的Vector，可以動態(tài)擴展大小，當大小超過容量時，重新分配一塊內(nèi)存，然后將數(shù)據(jù)復制到新的內(nèi)存區(qū)域。下面我們通過幾個問題來更好理解golang 的數(shù)組和切片，一起來看看吧。

一、類型

數(shù)組是值類型，將一個數(shù)組賦值給另一個數(shù)組時，傳遞的是一份拷貝。

切片是引用類型，切片包裝的數(shù)組稱為該切片的底層數(shù)組。

我們來看一段代碼

//a是一個數(shù)組，注意數(shù)組是一個固定長度的，初始化時候必須要指定長度，不指定長度的話就是切片了
a := [3]int{1, 2, 3}
//b是數(shù)組，是a的一份拷貝
b := a
//c是切片，是引用類型，底層數(shù)組是a
c := a[:]
for i := 0; i < len(a); i++ {
 a[i] = a[i] + 1
}
//改變a的值后，b是a的拷貝，b不變，c是引用，c的值改變
fmt.Println(a) //[2,3,4]
fmt.Println(b) //[1 2 3]
fmt.Println(c) //[2,3,4]

二、make

make 只能用于slice, map 和 channel, 所以下面一段代碼生成了一個slice，是引用類型

s1 := make([]int, 0, 3)

for i := 0; i < cap(s1); i++ {
 s1 = append(s1, i)
}
s2 := s1
for i := 0; i < len(a); i++ {
 s1[i] = s1[i] + 1
}

fmt.Println(s1) //[1 2 3]
fmt.Println(s2) //[1 2 3]

三、當對slice append 超出底層數(shù)組的界限時

//n1是n2的底層數(shù)組
n1 := [3]int{1, 2, 3}
n2 := n1[0:3]
fmt.Println("address of items in n1: ")
for i := 0; i < len(n1); i++ {
 fmt.Printf("%p\n", &n1[i])
}
//address of items in n1:
//0xc20801e160
//0xc20801e168
//0xc20801e170
fmt.Println("address of items in n2: ")
for i := 0; i < len(n2); i++ {
 fmt.Printf("%p\n", &n2[i])
}
//address of items in n2:
//0xc20801e160
//0xc20801e168
//0xc20801e170

//對n2執(zhí)行append操作后，n2超出了底層數(shù)組n1的j
n2 = append(n2, 1)
fmt.Println("address of items in n1: ")
for i := 0; i < len(n1); i++ {
 fmt.Printf("%p\n", &n1[i])
}
//address of items in n1:
//0xc20801e160
//0xc20801e168
//0xc20801e170

fmt.Println("address of items in n2: ")
for i := 0; i < len(n2); i++ {
 fmt.Printf("%p\n", &n2[i])
}
//address of items in n2:
//0xc20803a2d0
//0xc20803a2d8
//0xc20803a2e0
//0xc20803a2e8

四、引用“失效”

實現(xiàn)了刪除slice最后一個item的函數(shù)

func rmLast(a []int) {
 fmt.Printf("[rmlast] the address of a is %p", a)
 a = a[:len(a)-1]
 fmt.Printf("[rmlast] after remove, the address of a is %p", a)
}

調(diào)用此函數(shù)后，發(fā)現(xiàn)原來的slice并沒有改變

func main() {
 xyz := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
 fmt.Printf("[main] the address of xyz is %p\n", xyz)
 rmLast(xyz)
 fmt.Printf("[main] after remove, the address of xyz is %p\n", xyz)
 fmt.Printf("%v", xyz) //[1 2 3 4 5 6 7 8 9]
}

打印出來的結(jié)果如下：

[main] the address of xyz is 0xc2080365f0
[rmlast] the address of a is 0xc2080365f0
[rmlast] after remove, the address of a is 0xc2080365f0
[main] after remove, the address of xyz is 0xc2080365f0
[1 2 3 4 5 6 7 8 9]

這里直接打印了slice的指針值，因為slice是引用類型，所以指針值都是相同的，我們換成打印slice的地址看下

func rmLast(a []int) {
 fmt.Printf("[rmlast] the address of a is %p", &a)
 a = a[:len(a)-1]
 fmt.Printf("[rmlast] after remove, the address of a is %p", &a)
}
func main() {
 xyz := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
 fmt.Printf("[main] the address of xyz is %p\n", &xyz)
 rmLast(xyz)
 fmt.Printf("[main] after remove, the address of xyz is %p\n", &xyz)
 fmt.Printf("%v", xyz) //[1 2 3 4 5 6 7 8 9]
}

結(jié)果：

[main] the address of xyz is 0xc20801e1e0
[rmlast] the address of a is 0xc20801e200
[rmlast] after remove, the address of a is 0xc20801e200
[main] after remove, the address of xyz is 0xc20801e1e0
[1 2 3 4 5 6 7 8 9]

這次可以看到slice作為函數(shù)參數(shù)傳入函數(shù)時，實際上也是拷貝了一份slice，因為slice本身是個指針，所以從現(xiàn)象來看，slice是引用類型

總結(jié)

以上就是這篇文章的全部內(nèi)容，希望對大家的學習或者工作帶來一定的幫助，如果有疑問大家可以留言交流。

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