go | 易学教程

Strange CSV result for quoted strings in go encoding/csv

阅读更多关于 Strange CSV result for quoted strings in go encoding/csv

问题 I have this little bit of code that kept me busy the whole weekend. package main import ( "encoding/csv" "fmt" "log" "os" ) func main() { f, err := os.Create("./test.csv") if err != nil { log.Fatal("Error: %s", err) } defer f.Close() w := csv.NewWriter(f) var record []string record = append(record, "Unquoted string") s := "Cr@zy text with , and \\ and \" etc" record = append(record, s) fmt.Println(record) w.Write(record) record = make([]string, 0) record = append(record, "Quoted string") s =

Using a variable in the struct tag

阅读更多关于 Using a variable in the struct tag

问题 How would I use a variable in a Go struct tag? This works: type Shape struct { Type string `json:"type"` } This does not work: const ( TYPE = "type" ) type Shape struct { Type string fmt.Sprintf("json:\"%s\"", TYPE) } In the first example, I am using a string literal, which works. In the second example, I am building a string using fmt.Sprintf , and I seem to be getting an error: syntax error: unexpected name, expecting } Here it is on the Go playground: https://play.golang.org/p/lUmylztaFg

Correct tile movement for a 2048 game

阅读更多关于 Correct tile movement for a 2048 game

问题 I decided to make a 2048 Command Line Edition but I'm having trouble getting the right tile movement... My current structure is that the board is a 2D array (4x4) of ints. When an input is received, it will try to push every tile in that direction (ignoring tiles with value 0), if it notices a change it will start over (Because a tile on the bottom row will have to go all the way up, not just one step up). However, a side effect of this is the following problem: [2][2][4] with the command ->

Correct tile movement for a 2048 game

阅读更多关于 Correct tile movement for a 2048 game

盘点Python列表生成式的三种方法

阅读更多关于盘点Python列表生成式的三种方法

点击上方“ Go语言进阶学习 ”，进行关注回复“ Go语言 ”即可获赠从入门到进阶共10本电子书今日鸡汤兴来每独往，胜事空自知。一、前言列表生成式即List Comprehensions，是Python内置的非常简单却强大的可以用来创建list的生成式。二、案例分析三种方法要生成list [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]可以用list(range(1, 11))。 print ( list (range( 1 , 11 ))) 如果要生成[1x1, 2x2, 3x3, …, 10x10]怎么做？ 1. 方法一是循环： L = [] for x in range ( 1 , 11 ): L. append (x * x) print (L) 但是循环太繁琐，而列表生成式则可以用一行语句代替循环生成上面的list： print ([x * x for x in range(1, 11)]) 写列表生成式时，把要生成的元素x * x放到前面，后面跟for循环，就可以把list创建出来，十分有用，多写几次，很快就可以熟悉这种语法。 for循环后面还可以加上if判断，这样就可以筛选出仅偶数的平方： for x in range ( 1 , 11 ): L. append (x * x) print ([x * x for x in

Compiler: too many arguments given despite that all are given

阅读更多关于 Compiler: too many arguments given despite that all are given

问题 I want to use the struct DataResponse as parameter for JSON() to respond with the user. By initializing an instance of DataResponse I get the error message, that too many arguments are given, but gave all that are necessary. type DataResponse struct { Status int `json:"status"` Data interface{} `json:"data"` } func GetUser(rw http.ResponseWriter, req *http.Request, ps httprouter.Params) { user := models.User{} // Fetching user from db resp := DataResponse(200, user) JSON(rw, resp) // rw is

Short circuit evaluation in Go

阅读更多关于 Short circuit evaluation in Go

问题 My understanding of short circuit evaluation is that an expression is only called when needed in an if statement. Does Go follow this? For instance, would I get better performance on average from: if !isValidQueryParams(&queries) || r == nil || len(queries) == 0 { return "", fmt.Errorf("invalid querystring") } ...to this: if r == nil || len(queries) == 0 || !isValidQueryParams(&queries) { return "", fmt.Errorf("invalid querystring") } ...since isValidQueryParams is a function with much more

Calling C function that requires sockaddr

阅读更多关于 Calling C function that requires sockaddr

问题 I have a C function that takes a sockaddr pointer. I've created a syscall.RawSockaddrInet4 object, but I cannot figure out how to cast the address of the object to a C.sockaddr pointer. I've tried this, (*syscall.RawSockaddr)(unsafe.Pointer(&sa)), but I get an error: cannot use (*syscall.RawSockaddr)(unsafe.Pointer(&sa)) (type *syscall.RawSockaddr) as type *C.struct_sockaddr in argument to _Cfunc_lib_connect Any ideas would be much appreciated! int lib_connect( int sock, enum lib_sock_type

why is this a deadlock in golang / waitgroup?

阅读更多关于 why is this a deadlock in golang / waitgroup?

问题 I'm not sure what I'm missing but I get a deadlock error. I'm using a buffered channel that I range over after all go routines complete. The channel has the capacity of 4 and I'm running 4 go routines so I'm expecting it to be "closed" automatically once it reaches the max capacity. package main import "fmt" import "sync" func main() { ch := make(chan []int, 4) var m []int var wg sync.WaitGroup for i := 0; i < 5; i++ { wg.Add(1) go func() { defer wg.Done() ch <- m return }() } wg.Wait() for c

How to update Mongodb fields with omitempty flag in Golang structure

阅读更多关于 How to update Mongodb fields with omitempty flag in Golang structure

问题 I am working on a Coupon form in which I have some optional fields. Introduction: All the form field values are received as JSON and mapped into a Golang structure. In the structure, I have added an "omitempty" flag with every field. So only those form values are mapped which have some appropriate value, rest of the values like 0, " ", false are ignored by the structure. Here is the Golang structure type Coupon struct { Id int `json:"id,omitempty" bson:"_id,omitempty"` Name string `json:"name