Go编程教程指南

\hGo编程语言指南。本指南涵盖了该语言的大部分重要特性，主要包Go流程控制语句：for、if、else和复杂类型：struct、slice和学习如何基于已有类型定义新的类型：本课涵盖了结构体、数组、slice作为语言的核心部分，Gogorouteinchannel，以及如何使用它们来实现不同的并发Go将并发作为语言的核心构成。本课将对其进行介绍，并提供了一些示例来Go程序都是由包组成的。\hpackagepackageimportfuncmain()fmt.Println("Myfavoritenumberis",packagepackageimportfuncmain()fmt.Printf("Nowyouhave%gproblems.",math.Nextafter(2,导🎧Go中，首字母大写的名称是被导出的。packagepackageimport(funcmain(){（参考\hGo语法定义的文章了解类型以这种形式出现的原因。packagepackageimportfuncadd(xint,yint)intreturnx+funcmain(){fmt.Println(add(42,13))Xint,y x,yx,yintx,ypackagepackageimportfuncadd(x,yint)intreturnx+funcmain(){fmt.Println(add(42,13))mutiple-packagepackageimportfuncswap(x,ystring)(string,string)returny,funcmain()a,b:=swap("hello","world")fmt.Println(a,b)Gopackagepackageimportfuncsplit(sumint)(x,yint){x=sum*4/9y=sum-funcmain(){packagepackageimportvarc,python,javafuncmain()varifmt.Println(i,c,python,packagepackageimportvari,jint=1,funcmain()varc,python,java=true,false,"no!"fmt.Println(i,j,c,python,java)packagepackageimportfuncmain()vari,jint=1,2k:=3c,python,java:=true,false,fmt.Println(i,j,k,c,python,Gointint8int16int32uintuint8uint16uint32uint64uintptrbyte//uint8的别名runeint32Unicodefloat32float64complex64complex128packagepackageimportvar MaxIntuint64==1<<64- complex128=cmplx.Sqrt(-5+funcmain()constf="%T(%v)\n"fmt.Printf(f,ToBe,ToBe)fmt.Printf(fmt.Printf(f,MaxInt,MaxInt)fmt.Printf(f,z,z)数值类型为布尔类型为packagepackageimportfuncmain()varivarffloat64varbboolvarsstringfmt.Printf("%v%v%v%q\n",i,f,b,CGo的在不同类型之间的项目赋值时需要显式转换。试着移除例float64int的转换看看会发生什么。packagepackageimportfuncmain()varx,yint=3,varffloat64=math.Sqrt(float64(x*x+varzint=int(f)fmt.Println(x,y,z)varvarivpackagepackageimportfuncmain()v:=42//changeme!fmt.Printf("visoftype%T\n",v)packagepackagemainimport"fmt"constPi=3.14funcmain()constWorld="世界"fmt.Println("Hello",World)fmt.Println("Happy"Pi"Day")constTruth=fmt.Println("Gorules?",packagepackageimportconst =1<<Small=Big>>funcneedInt(xint)int{returnx*10+1funcneedFloat(xfloat64)float64returnx*funcmain(){Go只有一种循环结构——`for`Java中做的一样，而`{}`packagepackageimportfuncmain(){sum:=0fori:=0;i<10;i++{sum+=iCJavafor-packagepackageimportfuncmain(){sum:=1for;sum<1000;{sum+=sumfor是Go的基于此可以省略分号：CwhileGo中叫做`for`packagepackageimportfuncmain(){sum:=1forsum<1000{sum+=sumpackagepackagefuncmain()forif语句除了没有了`()`之外（甚至强制不能使用它们），C（耳熟吗packagepackageimportfuncsqrt(xfloat64)stringifx<0returnsqrt(-x)+returnfuncmain(){fmt.Println(sqrt(2),sqrt(-4))packagepackageimportimportfuncpow(x,n,limfloat64)float64ifv:=math.Pow(x,n);v<limreturnreturnfuncmain(){pow(3,2,pow(3,3,ifpackagepackageimportfuncpow(x,n,limfloat64)float64ifv:=math.Pow(x,n);v<limreturn}elsefmt.Printf("%g>=%g\n",v,vreturnfuncfuncmain(){pow(3,2,pow(3,3,z常小）\hmath.Sqrt接近吗？packagepackageimportfuncSqrt(xfloat64)float64funcmain(){packagepackageimportfuncmain(){fmt.Print("Gorunson")switchos:=runtime.GOOS;oscase"darwin":fmt.Println("OSX.")case"linux"://freebsd,//plan9,windows...fmt.Printf("%s.",os)switch（switchswitchi{case0:casef():i==0`f`。注意：Goplayground2009-11-1023:00:00UTCpackagepackageimportfuncmain()fmt.Println("When'sSaturday?")today:=time.Now().Weekday()switchtime.Saturday{casetoday+0:casetoday+1:casetoday+2:fmt.Println("Intwodays.")fmt.Println("Toofarswitch`switchtrue`if-then-elsepackagepackageimportfuncmain()t:=t:=switchcaset.Hour()<12:fmt.Println("Goodmorning!")caset.Hour()<17:fmt.Println("Goodafternoon.")fmt.Println("Gooddeferpackagepackageimportfuncmain()defer阅读\h博文了解更多关于deferpackagepackageimportfuncfuncmain()fori:=0;i<10;i++deferGo类型*TT`nil`varp &ii:=p=fmt.Println(*pfmt.Println(*pp*p=通过指针p设置与C不同，Go没有指针运算。packagepackageimportfuncmain()i,j:=42,p:=//pointtofmt.Println(*p)//readithroughthe*p=21 //setithroughthepointerfmt.Println(i)//seethenewvalueofip=p= //pointto*p=*p/37 //dividejthroughthepointerfmt.Println(j)//seethenewvalueofjpackagepackageimporttypeVertexstructXintYfuncmain(){fmt.Println(Vertex{1,2})struct-packagepackageimporttypeVertexstructXintYfuncfuncmain()v:=Vertex{1,v.X=struct-packagepackageimporttypeVertexstructXintYfuncmain()v:=Vertex{1,2}p:=&vp.X=struct-packagepackageimporttypeVertexstruct{X,Yintvarv1=Vertex{1,2}//类型为Vertexv2=Vertex{X:1}//Y:0被省略v3=Vertex{} //X:0和Y:0p=&Vertex{12funcmain(){fmt.Println(v1,p,v2,v3)vara a约，但是请不要担心；Go提供了更加便利的方式来使用数组。packagepackageimportfuncmain()vara[2]stringa[0]="Hello"a[1]=fmt.Println(a[fmt.Println(a[0],a[1])slice[]TTslicepackagepackageimportfuncmain()p:=[]int{2,3,5,7,11,fmt.Println("p==",fori:=0;i<len(p);i++{fmt.Printf("p[%d]==%d\n",i,p[i])sliceslice值指向相同的数组。 lohi-1slice slicing-packagepackageimportfuncmain()p:=[]int{2,3,5,7,11,fmt.Println("p==",p)fmt.Println("p[1:4]==",p[1:4])0fmt.Println("p[:3]==",len(s)fmt.Println("p[4:]==",构造slicemakeslice指向a:=make([]int,5)// 为了指定容量，可传递第三个参数到bb:=make([]int,0,5)//len(b)=0,b=b[:cap(b)]//len(b)=5,b= //len(b)=4,packagepackageimportfuncmain()a:=make([]int,5)printSlice("a",a)bb:=make([]int,0,5)printSlice("b",b)c:=printSlice("c",c)d:=c[2:5]printSlice("d",funcprintSlice(sstring,x[]int){fmt.Printf("%slen=%dcap=%d%v\n",s,len(x),cap(x),slice`nil`nilslice0nil-packagepackageimportfuncmain()varzfmt.Println(z,len(z),ifz==nil{向slice添加元素sliceGo`append`\h文档appendfuncappend(s[]T,vs...T) appendsTT的值将会添加到slice。appendsliceslices的slice会指向这个新分配的数组。（slice\hslice：使用和内幕。packagepackageimportfuncmain()vara[]intprintSlice("a",a)//appendworksonnilslices.a=append(a,0)printSlice("a",a)//theslicegrowsasneeded.a=append(a,1)printSlice("a",a)//wecanaddmorethanoneelementatatime.a=append(a,2,3,4)printSlice("a",funcprintSlice(sstring,x[]int){fmt.Printf("%slen=%dcap=%d%v\n",s,len(x),cap(x),forrangeslicemappackagepackageimportvarpow=[]int{1,2,4,8,16,32,64,funcmain()fori,v:=rangepow{fmt.Printf("2**%d=%d\n",i,v)如果只需要索引值，去掉value”packagepackageimportfuncmain()pow:=make([]int,fori:=rangepow{pow[i]=1<<uint(i)for_,value:=rangepow{fmt.Printf("%d\n",value)实现`Pic`。它返回一个slice的长度`dy`，和slice中每个元素的长度的8`dx`。当执行这个程序，它会将整数转换为灰度（好吧，蓝度）图片的实现已经完成。可能用到的函数包括(x+y)/2x*y`x^y`（\h（需要使用循环来分配[][]uint8`[]uint8`。packagepackageimport"/p/go-funcPic(dx,dyint)[][]uint8funcmain(){mapmapmakenewnilmap是空packagepackageimporttypetypeVertexstruct{Lat,Longvarmmap[string]Vertexfuncmain(){m=make(map[string]Vertex)m["BellLabs"]=Vertex{40.68433,-fmt.Println(m["Bellmap的文法mappackagepackageimporttypeVertexstruct{Lat,Longfloat64varm=map[string]Vertex{"BellLabs":Vertex{40.68433,-"Google":Vertex{37.42202,-122.08408,funcmain(){的文法packagepackageimporttypeVertexstruct{Lat,Longfloat64varm="BellLabs":{40.68433,- {37.42202,-funcmain(){修改mapmm[key]= elem= delete(m, elem,ok= keym中，`ok`trueok`false`elemmapmap的元素类型的零packagepackageimportfuncmain()m:=m["Answer"]=fmt.Println("Thevalue:",m["Answer"]=fmt.Println("Thevalue:",delete(m,fmt.Println("Thevalue:",v,ok:=fmt.Println("Thevalue:",v,"Present?",`WordCount`s“词”map\hstrings.Fieldspackagepackageimport"/p/go-funcWordCount(sstring)map[string]intreturnmap[string]int{"x":funcmain(){packagepackageimportfuncmain()hypot:=func(x,yfloat64)float64returnmath.Sqrt(x*x+fmt.Println(hypot(3,Go函数可以是闭包的。闭包是一个函数值，它来自函数体的外部的变量引“绑定”在这packagepackageimportfuncadder()func(int)int{sum:=0returnfunc(xint)int{sum+=xreturnfuncmain()pos,neg:=adder(),fori:=0;i<10;i++{packagepackageimportfibonacciintfuncfibonacci()func()intfuncmain()f:=f:=fori:=0;i<10;i++{GopackagepackageimporttypeVertexstruct{X,Yfloat64func(v*Vertex)Abs()float64returnmath.Sqrt(v.X*v.X+funcmain()v:=&Vertex{3,4}packagepackageimporttypeMyFloatfunc(fMyFloat)Abs()float64iff<0returnfloat64(-returnfuncmain()f:=MyFloat(-math.Sqrt2)MyFloatAbsScaleVertex代替*Vertex作为接收vVertexScale方法没有任何作用。`Scale``v`vAbs`v`。所以读取的是原始值（通packagepackageimporttypeVertexstruct{X,Yfloat64func(v*Vertex)Scale(ffloat64)v.X=v.X*v.Y=v.Y*func(v*Vertex)Abs()float64returnmath.Sqrt(v.X*v.X+funcmain()v:=&Vertex{3,4}fmt.Println(v,v.Abs())注意：例子代码的加粗标红Abs只定义在（指针类型）Vertex（值类型）`Abser`packageimporttypeAbserinterface{Abs()float64funcmain()varaf:=MyFloat(-math.Sqrt2)v:=Vertex{3,4}a=f//aMyFloat实现了Absera&va*Vertex实现了下面一行，vVertex（AbsertypeMyFloatfunc(fMyFloat)Abs()float64iff<0returnfloat64(-returntypeVertexstruct{X,Yfloat64func(v*Vertex)Abs()float64returnmath.Sqrt(v.X*v.X+\hioReader`Writer`packagepackageimporttypeReaderinterfaceRead(b[]byte)(nint,errtypeWriterinterfaceWrite(b[]byte)(nint,errtypeReadWriterinterface{funcmain()varwos.StdoutWriterw=os.Stdoutfmt.Fprintf(w,"hello,\h\htypetypeStringerinterface{String()stringStringer是一个可以用字符串描述自己的类型。`fmt`（还有许多其他packagepackageimporttypePersonstruct{NamestringAgefunc(pPerson)String()stringreturnfmt.Sprintf("%v(%vyears)",p.Name,funcmain()a:=Person{"ArthurDent",z:=Person{"ZaphodBeeblebrox",9001}fmt.Println(a,z)例如，`IPAddr{1,`2,`3,`4}`应当输出`""`。packagepackageimporttypeIPAddr//TODO:Adda"String()string"methodtofuncmain()addrs:=map[string]IPAddr{"loopback":{127,0,0,1},"googleDNS":{8,8,8,forn,a:=rangeaddrs{fmt.Printf("%v:%v\n",n,a)Goerrorfmt.Stringer类似，`error`typetypeerrorinterface{Error()string（fmt.Stringer类似，`fmt``error`。`nil`i,i,err:=strconv.Atoi("42")iferr!=nil{fmt.Printf("couldn'tconvertnumber:%v\n",fmt.Println("Convertedinteger:",errornilnilerrorpackagepackageimporttypeMyErrorstruct{Whentime.TimeWhatstringfunc(e*MyError)Error()stringreturnfmt.Sprintf("at%v,%s",e.When,e.What)funcrun()errorreturn&MyError{"itdidn'tfuncmain()iferr:=run();err!=nil{Sqrtnil的错误值。复数同样也不被支typetypeErrNegativeSqrtfuncfunc(eErrNegativeSqrt)Error()`error`ErrNegativeSqrt(-`"cannotSqrtnegativenumber:2"`packagepackageimportfuncSqrt(xfloat64)(float64,error)return0,funcmain(){ioio.ReaderGo标准库包含了这个接口的\h许多实现func(T)Read(b[]byte)(nint,err Readslice\hstrings.Reader8字节的速度读取它packagepackageimportfuncmain()r:=strings.NewReader("Hello,b:=make([]byte,forn,err:=fmt.Printf("n=%verr=%vb=%v\n",n,err,b)fmt.Printf("b[:n]=%q\n",b[:n])iferr==io.EOFReaderASCII字符'A'packagepackageimport"/p/go-typeMyReader//TODO:AddaRead([]byte)(int,error)methodtofuncmain(){\hio.Reader`io.Reader`，然后通过某种形式修改数例如，\hgzip.NewReader`io.Reader`（压缩的数据流）并且返回同样io.Reader的`*gzip.Reader`（解压缩后的数据流）。io.Reader`rot13Reader`io.Reader\hrot13Read`io.Reader`packagepackageimport(typerot13Readerstruct{rio.Readerfuncmain()ss:=strings.NewReader("Lbhpenpxrqgurpbqr!")r:=rot13Reader{s}io.Copy(os.Stdout,服务器\hhttphttp.HandlerHTTPpackagepackagetypeHandlerinterfaceServeHTTP(wResponseWriter,rHello`http.Handler`。\hhttp://localhost:4000/会看到来自程序的问候。web的指南用户界面运行。为了尝试编写服务器，可能需要\hGoweb-packagepackageimporttypeHellofunc(hHello)ServeHTTP(whttp.ResponseWriter,r*http.Request){fmt.Fprint(w,"Hello!")funcmain()varherr:=http.ListenAndServe(err:=http.ListenAndServe("localhost:4000",iferr!=nil{处理ServeHTTPweb服务器中注册它typetypeStringtypeStructstruct{Greetingstring http.Handle("/string",String("I'mafrayedknot."))http.Handle("/struct",http.Handle("/string",String("I'mafrayedknot."))http.Handle("/struct",&Struct{"Hello",":","Gophers!"})webweb服务，你可能需要\h安装Go。packagepackageimportfuncmain()//yourhttp.Handlecallsherelog.Fatal(http.ListenAndServe("localhost:4000",nil))\hPackageimageImagepackagepackagetypeImageinterface{ColorModel()color.ModelBounds()RectangleAt(x,yint)*注意*：`Bounds`Rectangle\himage.Rectangleimage（参阅\h文档了解全部信息。\himage/color包packagepackageimportfuncmain()m:=image.NewRGBA(image.Rect(0,0,100,100))fmt.Println(m.At(0,image.ImagesliceImage类型，要实现\h必要的方法`pic.ShowImage`Bounds`image.Rectangle``image.Rect(0,0w,h)`ColorModel`color.RGBAModel``color.RGBA{v,v,255,255}`packagepackageimport"/p/go-typeImagestruct{}funcmain(){m:=Image{}goroutineGogogof(x,y,goroutinef(x,f(x,y,fxyzgoroutinegoroutine`f`goroutine在相同的地址空间中运行，因此访问共享内存必须进行同步。\hGo中并不经常用到，因为有其他的办法。（在接下packagepackageimportfuncsay(sstring)fori:=0;i<5;i++{time.Sleep(100*time.Millisecond)funcmain()gosay("world")channelchannel操作符<-chch vchannelchvchchvmapslice一样，channelch:=make(chan packagepackageimportfuncsum(a[]int,cchanint){sum:=0for_,v:=rangea{sum+=vcsum将和送入funcmain()a:=[]int{7,2,8,-9,4,c:=make(changosum(a[:len(a)/2],gosum(a[len(a)/2:],xyc,<-ccfmt.Println(x,y,缓冲channel_带缓冲的_make提供第二个参数作为缓冲长度来初始化一个缓冲channel：ch:=make(chanint, channel发送数据的时候，只有在缓冲区满的时候才会阻塞。当缓冲区buffered-packagepackageimportfuncmain()c:=make(chanint,2)c<-1c<-range和closechannel来表示再没有值会被发送了。接收者可以通过赋值语句的第二参数来测试channel是否被关闭：当没有值可以接收并且channelv,ok:=<- ok`false``forirangec`channel注意：只有发送者才能关闭channel，而不是接收者。向一个已经关闭的channelpanic。还要注意：channel与文件不同；通常情况关闭，例如中断一个`range`。packagepackageimportfuncfibonacci(nint,cchanint){x,y:=0,1fori:=0;i<n;i++{c<-xx,y=y,funcmain()c:=make(chanint,10)gofibonacci(cap(c),c)fori:=rangec{selectgoroutinepackagepackageimportfuncfuncfibonacci(c,quitchanint){x,y:=0,1forselectcasec<-x,y=y,case<-quit:funcmain()c:=make(chanint)quit:=make(chanint)gofunc(){fori:=0;i<10;i++{quit<-fibonacci(c,select中的其他条件分支都没有准备好的时候，`default`selectselectcasei:=<-i从cpackagepackageimportfuncmain()tick:=time.Tick(100*time.Millisecond)boom:=time.After(500*time.Millisecond)for{selectcase<-tick:case<-boom: time.Sleep(50*time.Millisecond)叉树保存了序列