Golang 中的范围关键字
在 Golang 范围内关键字用于不同类型的数据结构，以便迭代元素。范围关键字主要用于 for 循环，以便迭代一个 地图切片通道 或一个 数组 的所有元素。当它遍历数组的元素并进行切片时，它以整数形式返回元素的索引。当它遍历一个映射的元素时，它返回下一个键值对的键。此外，范围可以返回一个值或两个值。让我们看看在 Golang 中迭代不同种类的集合时范围返回什么。
- Array or slice: In the case of array or slice, the first value returned is index , and the second value is element .
- String: The first value returned in the string is index , and the second value is rune int .
- Map: The first value returned in the map is the key , and the second value is the value of the key-value pair in the map.
- Channel: The first value returned in the channel is element , and the second value is none .
现在我们来看一些例子来说明 range 关键字在 Golang 中的用法。
例 1:
// Golang Program to illustrate the usage
// of range keyword over items of an
// array in Golang
package main
import "fmt"
// main function
func main() {
// Array of odd numbers
odd := [7]int{1, 3, 5, 7, 9, 11, 13}
// using range keyword with for loop to
// iterate over the array elements
for i, item := range odd {
// Prints index and the elements
fmt.Printf("odd[%d] = %d \n", i, item)
}
}
输出:
odd[0] = 1
odd[1] = 3
odd[2] = 5
odd[3] = 7
odd[4] = 9
odd[5] = 11
odd[6] = 13
这里，所有元素都打印有各自的索引。
例 2:
// Golang Program to illustrate the usage of
// range keyword over string in Golang
package main
import "fmt"
// Constructing main function
func main() {
// taking a string
var string = "GeeksforGeeks"
// using range keyword with for loop to
// iterate over the string
for i, item := range string {
// Prints index of all the
// characters in the string
fmt.Printf("string[%d] = %d \n", i, item)
}
}
输出:
string[0] = 71
string[1] = 101
string[2] = 101
string[3] = 107
string[4] = 115
string[5] = 102
string[6] = 111
string[7] = 114
string[8] = 71
string[9] = 101
string[10] = 101
string[11] = 107
string[12] = 115
这里打印的项目是符文，即构成字符串的所述字符的 int32 ASCII 值。
例 3:
// Golang Program to illustrate the usage of
// range keyword over maps in Golang
package main
import "fmt"
// main function
func main() {
// Creating map of student ranks
student_rank_map := map[string]int{"Nidhi": 3,
"Nisha": 2, "Rohit": 1}
// Printing map using keys only
for student := range student_rank_map {
fmt.Println("Rank of", student, "is: ",
student_rank_map[student])
}
// Printing maps using key-value pair
for student, rank := range student_rank_map {
fmt.Println("Rank of", student, "is: ", rank)
}
}
输出:
Rank of Nidhi is: 3
Rank of Nisha is: 2
Rank of Rohit is: 1
Rank of Nidhi is: 3
Rank of Nisha is: 2
Rank of Rohit is: 1
因此，这里首先只使用键打印输出，然后再次使用键和值打印输出。
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