英文:
Go template/html iteration to generate table from struct
问题
给定一个结构体的集合，我该如何使用“range”模板迭代器打印出一个表格，每个结构体对应一行，每个字段值对应一列，而不需要显式命名字段？
container := []Nodetype Node struct {Contact_id intEmployer_id intFirst_name stringMiddle_name stringLast_name string}模板代码：{{range .container}}<tr><td>{{.Prefix}}</td><td>{{.First_name}}</td><td>{{.Middle_name}}</td><td>{{.Last_name}}</td><td>{{.Contact_id}}</td><td>{{.Employer_id}}</td></tr>{{end}}------------------------当我尝试使用以下方式迭代值时：{{range .container}}{{range .}}<td>{{.}}</td>{{end}}{{end}}我被告知不能迭代值。有没有一种简洁的方法来实现这个？<details><summary>英文:</summary>Given a collection of structs, how can I use the "range" template iterator to print out a table that assigns a row per struct, and a column per field value without explicity naming the fields?container := []Nodetype Node struct {Contact_id intEmployer_id intFirst_name stringMiddle_name stringLast_name string}Template Code:{{range .container}}<tr><td>{{.Prefix}}</td><td>{{.First_name}}</td><td>{{.Middle_name}}</td><td>{{.Last_name}}</td><td>{{.Contact_id}}</td><td>{{.Employer_id}}</td></tr>{{end}}------------------------When I try iterating through the values using{{range .container}}{{range .}}<td>{{.}}</td>{{end}}{{end}}I am told that I cannot iterate over the Values.Is there any clean way to do this?</details># 答案1**得分**: 16使用`html/template`包时，无法迭代结构体中的字段。在该包的[文档](http://golang.org/pkg/text/template/)中，可以阅读到以下内容：>{{range pipeline}} T1 {{end}}>管道的值必须是数组、切片、映射或通道。也就是说，管道不能是结构体。你可以采取以下方法之一：* 使用中间类型，例如`[][]interface{}`，作为传递给模板的容器变量* 将每个`<td>`单元格分别输出，就像你展示的那样* 创建一个模板函数，将结构体值转换为可迭代的某种类型由于结构体在编译时定义，并且在运行时不会改变其结构，因此迭代是不必要的，也不会使模板更清晰。我建议不要这样做。**编辑**但有时反射是一件好事。Brenden还指出，实际上可以让`range`迭代从函数返回的值。如果使用反射，这将是最简单的方法。使用模板函数的完整工作示例：package mainimport ("html/template""os""reflect")type Node struct {Contact_id intEmployer_id intFirst_name stringMiddle_name stringLast_name string}var templateFuncs = template.FuncMap{"rangeStruct": RangeStructer}// 在模板中，我们使用rangeStruct将结构体值转换为可迭代的切片var htmlTemplate = `{{range .}}<tr>{{range rangeStruct .}} <td>{{.}}</td>{{end}}</tr>{{end}}`func main() {container := []Node{{1, 12, "Accipiter", "ANisus", "Nisus"},{2, 42, "Hello", "my", "World"},}// 创建模板并注册模板函数t := template.New("t").Funcs(templateFuncs)t, err := t.Parse(htmlTemplate)if err != nil {panic(err)}err = t.Execute(os.Stdout, container)if err != nil {panic(err)}}// RangeStructer接受第一个参数（必须是结构体）并将每个字段的值返回为切片。如果没有参数或第一个参数不是结构体，则返回nil。func RangeStructer(args ...interface{}) []interface{} {if len(args) == 0 {return nil}v := reflect.ValueOf(args[0])if v.Kind() != reflect.Struct {return nil}out := make([]interface{}, v.NumField())for i := 0; i < v.NumField(); i++ {out[i] = v.Field(i).Interface()}return out}输出：<tr><td>1</td><td>12</td><td>Accipiter</td><td>ANisus</td><td>Nisus</td></tr><tr><td>2</td><td>42</td><td>Hello</td><td>my</td><td>World</td></tr>[Playground](http://play.golang.org/p/38W6Lw3zSE)<details><summary>英文:</summary>With the `html/template`, you cannot iterate over the fields in a struct. In the [documentation](http://golang.org/pkg/text/template/) for the package, you can read:>{{range pipeline}} T1 {{end}}>The value of the pipeline must be an array, slice, map, or channel.That is, Pipeline cannot be a struct. Either you need to:* use an intermediate type, eg. `[][]interface{}`, as container variable that you pass to the template* type out each <td> cell separately as you've shown* create a template function that converts struct values to some type you can iterate overSince a struct is defined at compile-time and won't change its structure during runtime, iteration is not necessary and wouldn't make things more clear in the template. I would advise against it.**Edit**But sometimes reflection is a good thing. Brenden also pointed out that you can actually let range iterate over the value returned from a function. If using reflection, this would be the easiest approach.Full working example using a template function:package mainimport ("html/template""os""reflect")type Node struct {Contact_id intEmployer_id intFirst_name stringMiddle_name stringLast_name string}var templateFuncs = template.FuncMap{"rangeStruct": RangeStructer}// In the template, we use rangeStruct to turn our struct values// into a slice we can iterate overvar htmlTemplate = `{{range .}}<tr>{{range rangeStruct .}} <td>{{.}}</td>{{end}}</tr>{{end}}`func main() {container := []Node{{1, 12, "Accipiter", "ANisus", "Nisus"},{2, 42, "Hello", "my", "World"},}// We create the template and register out template functiont := template.New("t").Funcs(templateFuncs)t, err := t.Parse(htmlTemplate)if err != nil {panic(err)}err = t.Execute(os.Stdout, container)if err != nil {panic(err)}}// RangeStructer takes the first argument, which must be a struct, and// returns the value of each field in a slice. It will return nil// if there are no arguments or first argument is not a structfunc RangeStructer(args ...interface{}) []interface{} {if len(args) == 0 {return nil}v := reflect.ValueOf(args[0])if v.Kind() != reflect.Struct {return nil}out := make([]interface{}, v.NumField())for i := 0; i < v.NumField(); i++ {out[i] = v.Field(i).Interface()}return out}Output:<tr><td>1</td><td>12</td><td>Accipiter</td><td>ANisus</td><td>Nisus</td></tr><tr><td>2</td><td>42</td><td>Hello</td><td>my</td><td>World</td></tr>[Playground](http://play.golang.org/p/38W6Lw3zSE)</details>
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