Example
One can declare and initialize a map in a single statement using a composite literal.
Using automatic type Short variable declaration:
mapIntInt := map[int]int{10: 100, 20: 100, 30: 1000}
mapIntString := map[int]string{10: "foo", 20: "bar", 30: "baz"}
mapStringInt := map[string]int{"foo": 10, "bar": 20, "baz": 30}
mapStringString := map[string]string{"foo": "one", "bar": "two", "baz": "three"}
The same code, but with Variable types:
var mapIntInt = map[int]int{10: 100, 20: 100, 30: 1000}
var mapIntString = map[int]string{10: "foo", 20: "bar", 30: "baz"}
var mapStringInt = map[string]int{"foo": 10, "bar": 20, "baz": 30}
var mapStringString = map[string]string{"foo": "one", "bar": "two", "baz": "three"}
You can also include your own structs in a map:
You can use custom types as value:
// Custom struct types
type Person struct {
FirstName, LastName string
}
var mapStringPerson = map[string]Person{
"john": Person{"John", "Doe"},
"jane": Person{"Jane", "Doe"}}
mapStringPerson := map[string]Person{
"john": Person{"John", "Doe"},
"jane": Person{"Jane", "Doe"}}
Your struct can also be the key to the map:
type RouteHit struct {
Domain string
Route string
}
var hitMap = map[RouteHit]int{
RouteHit{"example.com","/home"}: 1,
RouteHit{"example.com","/help"}: 2}
hitMap := map[RouteHit]int{
RouteHit{"example.com","/home"}: 1,
RouteHit{"example.com","/help"}: 2}
You can create an empty map simply by not entering any value within the brackets {}.
mapIntInt := map[int]int{}
mapIntString := map[int]string{}
mapStringInt := map[string]int{}
mapStringString := map[string]string{}
mapStringPerson := map[string]Person{}
You can create and use a map directly, without the need to assign it to a variable. However, you will have to specify both the declaration and the content.
// using a map as argument for fmt.Println()
fmt.Println(map[string]string{
"FirstName": "John",
"LastName": "Doe",
"Age": "30"})
// equivalent to
data := map[string]string{
"FirstName": "John",
"LastName": "Doe",
"Age": "30"}
fmt.Println(data)
