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📜  Go语言-范围

📅  最后修改于: 2020-11-04 08:06:35             🧑  作者: Mango

 

range关键字在for循环中用于迭代数组，切片，通道或映射的项。对于数组和切片，它以整数形式返回项目的索引。对于地图，它返回下一个键值对的键。范围返回一个或两个值。如果在范围表达式的左侧仅使用一个值，则它是下表中的第一个值。

Range expression 1st Value 2nd Value(Optional)
Array or slice a [n]E index i int a[i] E
String s string type index i int rune int
map m map[K]V key k K value m[k] V
channel c chan E element e E none

例

以下段落显示了如何使用范围-

现场演示
package main

import "fmt"

func main() {
   /* create a slice */
   numbers := []int{0,1,2,3,4,5,6,7,8} 
   
   /* print the numbers */
   for i:= range numbers {
      fmt.Println("Slice item",i,"is",numbers[i])
   }
   
   /* create a map*/
   countryCapitalMap := map[string] string {"France":"Paris","Italy":"Rome","Japan":"Tokyo"}
   
   /* print map using keys*/
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
   
   /* print map using key-value*/
   for country,capital := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",capital)
   }
}

编译并执行上述代码后，将产生以下结果-

Slice item 0 is 0
Slice item 1 is 1
Slice item 2 is 2
Slice item 3 is 3
Slice item 4 is 4
Slice item 5 is 5
Slice item 6 is 6
Slice item 7 is 7
Slice item 8 is 8
Capital of France is Paris
Capital of Italy is Rome
Capital of Japan is Tokyo
Capital of France is Paris
Capital of Italy is Rome
Capital of Japan is Tokyo