Go Map

by Online Tutorials Library July 14, 2022

Go Map

In Go, Maps is an unordered collection of key and its associated value. They are very good for looking up values fast. The key type must have the operations == and != defined, like string, int, float.

Hence arrays, slices and structs cannot be used as key type, but pointers and interface types can.

structs can be used as a key when we provide Key() or Hash() method, so that a unique numeric or string key can be calculated from the struct’s fields.

A map is a reference type and declared in general as:

e.g.

Go Map Example

 package main import “fmt” func main ()  {    x := map[string]int{“Kate”:28,”John”:37, “Raj”:20}    fmt.Print(x)    fmt.Println(“n”,x[“Raj”]) } 

Output:

map[John:37 Raj:20 Kate:28]  20

Go Map Insert and Update operation

Update and insert operation are similar in go map. If the map does not contain the provided key the insert operation will takes place and if the key is present in the map then update operation takes place.

 package main import “fmt” func main() {    m := make(map[string]int)    fmt.Println(m)    m[“Key1”] = 10    m[“Key2”] = 20    m[“Key3”] = 30    fmt.Println(m)    m[“Key2”] = 555    fmt.Println(m) } 

Output:

map[] map[Key3:30 Key1:10 Key2:20] map[Key1:10 Key2:555 Key3:30]

Go Map Delete operation

You can delete an element in Go Map using delete() function.

Syntax:

Example:

 package main import “fmt” func main() {    m := make(map[string]int)    m[“Key1”] = 10    m[“Key2”] = 20    m[“Key3”] = 30    fmt.Println(m)    delete(m, “Key3”)    fmt.Println(m) } 

Output:

map[Key1:10 Key2:20 Key3:30] map[Key2:20 Key1:10]

Go Map Retrieve Element

Syntax:

Example:

 package main import “fmt” func main() {    m := make(map[string]int)    m[“Key1”] = 10    m[“Key2”] = 20    m[“Key3”] = 30    fmt.Println(m)    fmt.Println(“The value:”, m[“Key2”]) } 

Output:

map[Key1:10 Key2:20 Key3:30] The value: 20

We can also test if a key is present in the table with two value example

syntax:

If key is not present, then the value of elem is the default value of element type.

If the type of elem is int then value of elem is zero.

 package main import “fmt” func main() {    m := make(map[string]int)    m[“Key1”] = 10    m[“Key2”] = 20    m[“Key3”] = 30    fmt.Println(m)    v, ok := m[“Key2”]    fmt.Println(“The value:”, v, “Present?”, ok)    i, j := m[“Key4”]    fmt.Println(“The value:”, i, “Present?”, j) } 

Output:

map[Key1:10 Key2:20 Key3:30] The value: 20 Present? true The value: 0 Present? false

In Go, Maps are like struct, but it requires keys

Go Map of Struct

 package main import “fmt” type Vertex struct {    Latitude, Longitude float64 } var m = map[string]Vertex{    “tutoraspire”: Vertex{     40.68433, -74.39967,   },    “SSS-IT”: Vertex{     37.42202, -122.08408,  }, } func main() {    fmt.Println(m) } 

Output:

map[tutoraspire:{40.68433 -74.39967} SSS-IT:{37.42202 -122.08408}]

Next TopicGo Error

Go Map

Go Map

Go Map Example

Go Map Insert and Update operation

Go Map Delete operation

Go Map Retrieve Element

Go Map of Struct

Install Git on Linux/Ubuntu

Buttons in Godot

You may also like