CODEWITHSUNDEEP
algorithmtemplatesgo
Johnson
Johnson

Reputation: 146

golang multiplication algorithm in html template

I am new for golang. I met a problem when I use multiplication in html/template. Some code like below.

template code: 

 {{range $i,$e:=.Items}}
      <tr>
           <td>{{add $i (mul .ID .Number)}}</td>
           <td>{{.Name}}</td>
      </tr>
  {{end}}

.go code

type Item struct{
        ID int
        Name string
    }
func init() {
    itemtpl,_:=template.New("item.gtpl").
        Funcs(template.FuncMap{"mul": Mul, "add": Add}).
        ParseFiles("./templates/item.gtpl")
}

func itemHandle(w http.ResponseWriter, req *http.Request) {

    items:=[]Item{Item{1,"name1"},Item{2,"name2"}}
    data := struct {
            Items []Item
            Number int
            Number2 int
        }{
            Items:    items,
            Number:   5,
            Number2:  2,
        }
        itemtpl.Execute(w, data)
}
func Mul(param1 int, param2 int) int {
    return param1 * param2
}
func Add(param1 int, param2 int) int {
    return param1 + param2
}

It will output nothing when I use the code above. But It will output 10 when I use the code outside of array below.

<html>
<body>
    {{mul .Number .Number2}}
</html>
</body>

I google a lot. I cannot find the usable like mine. I want to use multiplication in array inside of html/template. Can someone tell me what is wrong with my code?

Upvotes: 5

Views: 4722

Answers (1)

icza
icza

Reputation: 418505

template.Execute() returns an error, you should always check that. Would you have done so:

template: item.gtpl:3:33: executing "item.gtpl" at <.Number>: Number is not a field of struct type main.Item

The "problem" is that {{range}} changes the pipeline (the dot, .) to the current item, so inside the {{range}}:

{{add $i (mul .ID .Number)}}

.Number will refer to a field or method of your Item type since you are looping over a []Item. But your Item type has no such method or field.

Use $.Number which will refer to the "top-level" Number and not a field of the current Item value:

{{add $i (mul .ID $.Number)}}

Try your modified, working code on the Go Playground.

$ is documented at text/template:

When execution begins, $ is set to the data argument passed to Execute, that is, to the starting value of dot.

Upvotes: 3

Related Questions