1. Basic use
package main
import (
"fmt"
)
func main() {
stu := make(map[string]int, 2)
stu["xiaoming"] = 25
stu["xiaohua"] = 23
(stu)
(stu["xiaoming"])
("type of a: %T", stu)
}
Output:
map[xiaohua:23 xiaoming:25]
25
type of a: map[string]int
2. Initialize together while declaring
package main
import (
"fmt"
)
func main() {
stu := map[string]int{
"xiaoming": 25,
"xiaohua": 22,
}
(stu)
(stu["xiaoming"])
(stu["xiaohua"])
}
Output:
map[xiaohua:22 xiaoming:25]
25
22
3. Determine whether the key exists
package main
import (
"fmt"
)
func main() {
stu := map[string]int{
"xiaoming": 25,
"xiaohua": 22,
}
v1, result1 := stu["xiaoming"]
v2, result2 := stu["xiaohuang"]
(result1, v1)
(result2, v2)
if result1 {
("yes")
} else {
("no")
}
if result2 {
("yes")
} else {
("no")
}
}
Output:
true 25
false 0
yes
no
If the key exists, result1 is true, otherwise, result2 can be seen.
4. Iterate over map
package main
import (
"fmt"
)
func main() {
stu := map[string]int{
"xiaoming": 25,
"xiaohua": 22,
"xiaozhang": 23,
"xiaoshi": 21,
"xiaoyu": 18,
}
for k, v := range stu {
(k, v)
}
}
Output:
xiaoming 25
xiaohua 22
xiaozhang 23
xiaoshi 21
xiaoyu 18
You can also just traverse the key
for k := range stu {
(k)
}
5. Delete the k-v pair
Use the built-in delete function to delete
package main
import (
"fmt"
)
func main() {
stu := map[string]int{
"xiaoming": 25,
"xiaohua": 22,
"xiaozhang": 23,
"xiaoshi": 21,
"xiaoyu": 18,
}
(stu)
delete(stu, "xiaoshi")
(stu)
}
Output:
map[xiaohua:22 xiaoming:25 xiaoshi:21 xiaoyu:18 xiaozhang:23]
map[xiaohua:22 xiaoming:25 xiaoyu:18 xiaozhang:23]
It is unordered, how to make it traverse maps in the specified order
"Unordered traversal demonstration"
package main
import (
"fmt"
"math/rand"
"time"
)
func main() {
(().UnixNano())
var hostMap = make(map[string]string, 10)
for i := 0; i < 10; i++ {
key := ("host%02d", i)
value := (100)
ip := ("10.1.1.%d", value)
hostMap[key] = ip
}
for k, v := range hostMap {
(k, v)
}
}
Output:
host03 10.1.1.32
host00 10.1.1.0
host02 10.1.1.37
host05 10.1.1.97
host06 10.1.1.61
host07 10.1.1.62
host08 10.1.1.28
host09 10.1.1.40
host01 10.1.1.62
host04 10.1.1.70
Have you noticed it? Maps are disordered. Although host01-host09 is assigned to map in sequence, it is not ordered when traversing the values. Moreover, the order of each traversal is different.
"Implement orderly traversal"
package main
import (
"fmt"
"math/rand"
"sort"
"time"
)
func main() {
(().UnixNano())
var hostMap = make(map[string]string, 10)
for i := 0; i < 10; i++ {
key := ("host%02d", i)
value := (100)
ip := ("10.1.1.%d", value)
hostMap[key] = ip
}
var hostSlice = make([]string, 0, 200)
// Append the key in the hostMap to hostSlice (slice) for k := range hostMap {
hostSlice = append(hostSlice, k)
}
// Use the built-in sort function to sort the slice (hostSlice) (sorting based on key, and the key has just been appended to the slice) (hostSlice)
for _, k := range hostSlice {
(k, hostMap[k])
}
}
Output:
host00 10.1.1.87
host01 10.1.1.98
host02 10.1.1.93
host03 10.1.1.4
host04 10.1.1.1
host05 10.1.1.28
host06 10.1.1.11
host07 10.1.1.43
host08 10.1.1.31
host09 10.1.1.83
Store as element into slice
package main
import (
"fmt"
)
func main() {
// Create a slice that stores map type elements, with a maximum expansion capacity of 3 dataSlice := make([]map[string]string, 3)
(dataSlice)
("------------")
// Create a map with both key and value of string at the index 0 of the slice, with a capacity of 2 dataSlice[0] = make(map[string]string, 2)
// Assign map type data to the index 0 position of the slice, the key is user and the value is root dataSlice[0]["user"] = "root"
dataSlice[0]["pwd"] = "abc123"
(dataSlice)
("------------")
for i := range dataSlice {
(dataSlice[i])
}
("------------")
for i := range dataSlice {
(dataSlice[i]["user"], dataSlice[i]["pwd"])
}
}
Output:
[map[] map[] map[]]
------------
[map[pwd:abc123 user:root] map[] map[]]
------------
map[pwd:abc123 user:root]
map[]
map[]
------------
root abc123
In the above example, only the map element is stored at index 0 of the slice, and index 1 and 2 do not.
8. Slice as the value of the map, and the key of the map is a string
package main
import "fmt"
func main() {
// Declare the slice of the string type and initialize two values value := []string{"192.168.10.12", "10.1.1.23"}
//Declare the map of the key type as a string and the value type as a slice, and initialize a pair of keys and values data := map[string][]string{
"ip": value,
}
(data)
(data["ip"])
}
Output:
map[ip:[192.168.10.12 10.1.1.23]]
[192.168.10.12 10.1.1.23]
Value as map
package main
import "fmt"
func main() {
value := map[string]string{
"Manage IP": "10.1.2.39",
"Business IP": "192.168.12.56",
}
a := map[string]map[string]string{
"nginx": value,
}
(a)
(a["nginx"])
(a["nginx"]["Manage IP"])
(a["nginx"]["Business IP"])
}
Output:
map[nginx:map[Business IP:192.168.12.56 Management IP:10.1.2.39]]]
map[Business IP: 192.168.12.56 Management IP: 10.1.2.39]
10.1.2.39
192.168.12.56
This is the end of this article about 9 common examples of maps shared in Golang. For more related Golang map content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!