Golang text/template sequence range

Question

I am new in Golang. I have a problem when I want to make an HTML table using "text/template". I don't get any reference on how to make sequence numbers. What I have done so far:

<table>
    <thead>
        <tr>
            <td>#</td>
            <td>Name</td>
        </tr>
    </thead>
    <tbody>
        {{ range $index, $val := .MyList }}
        <tr>
            <td>{{ ??? }}</td>
            <td>{{ $val.Name }}</td>
        </tr>
        {{ end }}
    </tbody>
</table>

How I can get the number to start from 1? I have try {{ $index + 1 }} but get error. Please anyone can help me out?

Answer 1

Use a custom function:

package main

import (
    "html/template"
    "log"
    "os"
)

const tplDef = `
        {{ range $index, $val := .MyList }}
        <tr>
            <td>{{ $index | incr }}</td>
            <td>{{ $val.Name }}</td>
        </tr>
        {{ end }}
`

func main() {
    tpl := template.New("index")
    tpl.Funcs(map[string]interface{}{
        "incr": func(i int) int {
            return i + 1
        },
    })
    _, err := tpl.Parse(tplDef)
    if err != nil {
        log.Fatal(err)
    }

    type T struct {
        Name string
    }

    type Whatever struct {
        MyList []T
    }

    w := Whatever{
        MyList: []T{
            {Name: "foo"},
            {Name: "bar"},
            {Name: "baz"},
        },
    }

    err = tpl.Execute(os.Stdout, w)
    if err != nil {
        log.Fatal(err)
    }
}

Playground.