Go (golang) Tutorials - Maps

Published: 28 March 2018
on channel: Ambasoft Java

462

#golang #go #maps

Map - key value pairs (index and value associated with the index)
Un ordered collection
----
1. Creating a Map
2. Initializing a map
3. Maps and Slices - Slices can't be a key for a map, whereas they can be a value
4. Nil Map
5. Retrieve values from Map
6. Iterating a Map - For Range
7. Removing item from Map

mapdemo.go
----------
package main
import "fmt"
func main(){
a:=make(map[int]string) //Creating a map with integer key and string values

b:=map[int]string{1:"one",2:"two",3:"one"} //Initialize a map with key and value
//Maps will allow duplication in values but not in keys
fmt.Println(a)
fmt.Println(b)
}

mapslicedemo.go
-----------------
package main
import "fmt"
func main(){
a:=map[int][]string{} //Trying to create a map with key of type integer slice
//Map keys should not be slices
fmt.Println(a)
}

mapdeclaredemo.go
-----------------
package main
import "fmt"
func main(){
var b map[string]string //Declaration of map b - nil map (map is neither initialized nor created)

a:=map[string]string{}
a["name"]="Jack" //initialize map after declaration
a["address"]="2nd Street"
a["city"]="Coimbatore"

b["name"]="Ram"

fmt.Println(a)
fmt.Println(b)
}

mapfetchdemo.go
---------------
package main
import "fmt"
func main(){
address:=map[string]string{"street":"1st Street","city":"Coimbatore","country":"India"}
fmt.Println(address) //Prints the entire map contents
//I need to check whether a key "street" is available in the map, if so, fetch the value
value,result:=address["street"] //Lookup returns two values, 1.value of the map found in the key,2. boolean which says whether the key exists or not
if result {
fmt.Println(value)
}else {
fmt.Println("Key not found")
}

value1:=address["name"] //If a key is non-existent in a map, the value returned will be ""
if value1!="" {
fmt.Println(value1)
}else {
fmt.Println("Key not found")
}
}

iteratemapdemo.go
-----------------
package main
import "fmt"
func main(){
a:=map[string]string{"name":"Ram","state":"Tamilnadu"}
for k,v:=range a { //Iterating maps using for-range loop with key and values
fmt.Printf("Key is %s, and value is %s\n",k,v)
}
delete(a,"state") //Delete a key-value pair from the map
for k,v:=range a {
fmt.Printf("Key %s,Value %s\n",k,v)
}
}

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