Go 映射
Go提供了另一种重要的数据类型，称为map，它将唯一键映射到值。键是一个对象，你可以在以后使用它来检索值。给定键和值，你可以将值存储在Map对象中。值存储后，可以使用其键检索它。
定义地图
你必须使用make创建地图的功能。
/* declare a variable, by default map will be nil*/ var map_variable map[key_data_type]value_data_type /* define the map as nil map can not be assigned any value*/ map_variable = make(map[key_data_type]value_data_type)
例子
以下示例说明了如何创建和使用地图：
package main
import "fmt"
func main() {
var countryCapitalMap map[string]string
/* create a map*/
countryCapitalMap = make(map[string]string)
/* insert key-value pairs in the map*/
countryCapitalMap["France"] = "Paris"
countryCapitalMap["Italy"] = "Rome"
countryCapitalMap["Japan"] = "Tokyo"
countryCapitalMap["India"] = "New Delhi"
/* print map using keys*/
for country := range countryCapitalMap {
fmt.Println("Capital of",country,"is",countryCapitalMap[country])
}
/* test if entry is present in the map or not*/
capital, ok := countryCapitalMap["United States"]
/* if ok is true, entry is present otherwise entry is absent*/
if(ok){
fmt.Println("Capital of United States is", capital)
} else {
fmt.Println("Capital of United States is not present")
}
}编译并执行上述代码后，将产生以下结果：
Capital of India is New Delhi Capital of France is Paris Capital of Italy is Rome Capital of Japan is Tokyo Capital of United States is not present
delete()函数
delete()函数用于从地图中删除条目。它需要映射和要删除的对应密钥。例如：
package main
import "fmt"
func main() {
/* create a map*/
countryCapitalMap := map[string] string {"France":"Paris","Italy":"Rome","Japan":"Tokyo","India":"New Delhi"}
fmt.Println("Original map")
/* print map */
for country := range countryCapitalMap {
fmt.Println("Capital of",country,"is",countryCapitalMap[country])
}
/* delete an entry */
delete(countryCapitalMap,"France");
fmt.Println("Entry for France is deleted")
fmt.Println("Updated map")
/* print map */
for country := range countryCapitalMap {
fmt.Println("Capital of",country,"is",countryCapitalMap[country])
}
}编译并执行上述代码后，将产生以下结果：
Original Map Capital of France is Paris Capital of Italy is Rome Capital of Japan is Tokyo Capital of India is New Delhi Entry for France is deleted Updated Map Capital of India is New Delhi Capital of Italy is Rome Capital of Japan is Tokyo