Golang(5)Interface and Concurrence

Golang(5)Interface and Concurrence

2.6 Interface
Interface is a collection of methods.

Interface Type
Define the Interface

type Men interface {
SayHi()
Sing(lyrics string)
Guzzle(beerStein string)
}

type YoungChap interface {
SayHi()
Sing(song string)
BorrowMoney(amount float32)
}

type ElderlyGent interface {
SayHi()
Sing(song string)
SpendSalary(amount float32)
}

interface Value
Men interface variable can store the parameters who implement this interface,for example,Human,Student,Employee instances.

func main(){
mike := Student{Human{“Mike”,25,“222-222-xxx”},“MIT”,0.00}
sam := Employee{Human{“Sam”,36,“444-222-xxx”},“Golang Inc.”,1000}

var i Men //define a variable from Interface
i = mike // i can be a student
i.SayHi()

i = sam // i can be employee

//slice of Men,but different objects
x := make([]Men,2)
x[0],x[1] = mike,sam

for _,value := range x{
value.SayHi()
}
}

Empty interface
var a interface{}
a can stores all the different types of instances.

var i int = 5
s:=“hello sillycat”
a = i
a = s

interface Function Parameters
for example,fmt.Println can accept all the parameters who implement string interface

type Stringer interface{
String() string
}

package main
import (
“fmt”
“strconv"
)

type Human struct {
name string
age int
phone string
}

func (h Human) String() string {
return “<“ + h.name + “ - “ + strconv.Itoa(h.age) + “ years - phone: “ + h.phone + “>"
}

func main() {
Bob := Human{“Bob”,39,“000-7777-xxx”}
fmt.Println(“This Human is : “,Bob)
}

Type of Interface
We know that interface variable can hold all the instances who implement this interface,how will we know that which class is that instance?
Comma-ok
value,ok = element.(T) value is the value of the variable,ok is bool,lament is the interface variable,T is the type.

For example
list := make(List,3)
list[0] = 1
list[1] = “Hello”

for index,element := range list {
if value,ok := element.(int); ok {
fmt.Printf(“list[%d] is an int and its value is %dn”,index,value)
}
else if value,ok := element.(string); ok {
fmt.Printf(“list[%d] is a string and its value is %sn”,value)
}
}

switch Test
The same example as follow>
for index,element := range list {
switch value := element.(type) {
case int:
fmt.Printf(“list[%d] is an int and its value is %dn”,value)
case string:
fmt.Printf(“list[%d] is a string and its value is %sn”,value)
default:
fmt.Println(“list[%] is of a different type”,index)
}
}

element.(type) this can only be used in switch statement.

Inner Interface
type ReadWriter interface {
Reader
Writer
}

Reflect
Laws of Reflection
http://blog.golang.org/laws-of-reflection

2.7 Concurrence
goroutine
go key word can start a go routine

package main

import (
"fmt"
"runtime"
)

func say(s string) {
for i := 0; i < 5; i++ {
runtime.Gosched()
fmt.Println(s)
}
}

func main() {
go say("world") //开一个新的Goroutines执行
say("hello") //当前Goroutines执行
}

Channels
ci : = make(chan int)
cs := make(cha string)
cf := make(cha interface{})

ch <- v //send v to channel ch
v := <- ch //receive data from ch,give the value to v

package main

import "fmt"

func sum(a []int,c chan int) {
total := 0
for _,v := range a {
total += v
}
c <- total // send total to c
}

func main() {
a := []int{7,2,8,-9,4,0}

c := make(chan int)
go sum(a[:len(a)/2],c)
go sum(a[len(a)/2:],c)
x,y := <-c,<-c // receive from c

fmt.Println(x,y,x+y)
}

sparkworker1:easygo carl$ go run src/com/sillycat/easygoapp/main.go 17 -5 12

Buffered Channel
ch := make(chan type,value)

value == 0 // no buffer,block
value > 0 // buffer,no block

package main

import "fmt"

func main() {
c := make(chan int,5) //修改2为1就报错，修改2为3可以正常运行
c <- 1
c <- 2
fmt.Println(<-c)
fmt.Println(<-c)
}

Range and Close
for i := range c
close(c)

Select
…snip…

Expiration time
…snip…

Runtime Goruntine
Goexit,Gosched,NumCPU,NumGoroutine,GOMAXPROCS



References:
https://github.com/astaxie/build-web-application-with-golang/blob/master/ebook/02.6.md

golang 1~4
http://sillycat.iteye.com/admin/blogs/2037798
http://sillycat.iteye.com/admin/blogs/2047158
http://sillycat.iteye.com/admin/blogs/2052936
http://sillycat.iteye.com/admin/blogs/2052937

revel
http://revel.github.io/tutorial/index.html
http://www.cnblogs.com/ztiandan/archive/2013/01/17/2864498.html

martini
http://0value.com/build-a-restful-API-with-Martini
https://github.com/go-martini/martini
https://github.com/PuerkitoBio/martini-api-example

goweb
http://www.giantflyingsaucer.com/blog/?p=4673
https://github.com/stretchr/goweb

http://joshua.themarshians.com/hardcore-google-communicating-go.html

json-go
https://gobyexample.com/json
http://blog.golang.org/json-and-go