Map
Map is a data structure which implements a hash table.
Map is a simple key-value storage. Map offers fast lookups, adds and deletes.
Zero Value Table
Map don't explicitly check if a key is created or not, instead if a key doesn't exists it returns the default value of value type.
Data type and their Default Value
| Type | Default Value |
|---|---|
| Numeric type(int, float) | 0 |
| Boolean | false |
| String | "” (empty string) |
For Ex.
1package main
2
3import "fmt"
4
5func main() {
6 m1 := map[string]int{
7 "a": 1}
8 m2 := map[string]bool{
9 "a": true,
10 }
11
12 fmt.Printf("Value of key 'a' is %v\nValue of key 'b' is %v\n", m1["a"], m1["b"])
13 fmt.Printf("Value of key 'a' is %v\nValue of key 'b' is %v\n", m2["a"], m2["b"])
14}
Output
1Value of key 'a' is 1
2Value of key 'b' is 0
3Value of key 'a' is true
4Value of key 'b' is false
Check if key exist in a map or not
When value of the key is retrived from the map, it also returns a boolean value.
It is a widely used practice in golang to name ok to the boolean argument.
1package main
2
3import "fmt"
4
5func main() {
6 m1 := map[string]int{
7 "a": 1,
8 "b": 2,
9 }
10
11 value, ok := m1["a"]
12
13 fmt.Printf("Key 'a' exists %v and its value is %v\n", ok, value)
14
15 _, ok = m1["c"]
16
17 fmt.Printf("Key 'c' exists %v\n", ok)
18}
Output
1Key 'a' exists true and its value is 1
2Key 'c' exists false
Final Words
Map is a very powerful data structure. If order is not required then prefer map to array.