淺析Go語言編程當中映射和方法的基本使用

/* declare a variable, by default map will be nil*/
var map_variable map[key_data_type]value_data_type

/* define the map as nil map can not be assigned any value*/
map_variable = make(map[key_data_type]value_data_type)

package main

import "fmt"

func main {
   var coutryCapitalMap map[string]string
   /* create a map*/
   coutryCapitalMap = make(map[string]string)
  
   /* insert key-value pairs in the map*/
   countryCapitalMap["France"] = "Paris"
   countryCapitalMap["Italy"] = "Rome"
   countryCapitalMap["Japan"] = "Tokyo"
   countryCapitalMap["India"] = "New Delhi"
  
   /* print map using keys*/
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
  
   /* test if entry is present in the map or not*/
   captial, ok := countryCapitalMap["United States"]
   /* if ok is true, entry is present otherwise entry is absent*/
   if(ok){
      fmt.Println("Capital of United States is", capital) 
   }else {
      fmt.Println("Capital of United States is not present")
   }
}

Capital of India is New Delhi
Capital of France is Paris
Capital of Italy is Rome
Capital of Japan is Tokyo
Capital of United States is not present

package main

import "fmt"

func main {  
   /* create a map*/
   coutryCapitalMap := map[string] string {"France":"Paris","Italy":"Rome","Japan":"Tokyo","India":"New Delhi"}
  
   fmt.Println("Original map")  
  
   /* print map */
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
  
   /* delete an entry */
   delete(countryCapitalMap,"France");
   fmt.Println("Entry for France is deleted") 
  
   fmt.Println("Updated map")  
  
   /* print map */
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
}

Original Map
Capital of France is Paris
Capital of Italy is Rome
Capital of Japan is Tokyo
Capital of India is New Delhi
Entry for France is deleted
Updated Map
Capital of India is New Delhi
Capital of Italy is Rome
Capital of Japan is Tokyo

func (variable_name variable_data_type) function_name() [return_type]{
   /* function body*/
}
 package main

import (
   "fmt"
   "math"
)

/* define a circle */
type Circle strut {
   x,y,radius float64
}

/* define a method for circle */
func(circle Circle) area() float64 {
   return math.Pi * circle.radius * circle.radius
}

func main(){
   circle := Circle(x:0, y:0, radius:5)
   fmt.Printf("Circle area: %f", circle.area())
}

Circle area: 78.539816