如何使用文本/模板的预定义“调用”功能？

Question

I'm trying to understand how to use call function in text/template package. Here is example:

type Human struct {
    Name string
}

func (h *Human) Say(str string) string {
    return str
}

func main() {
    const letter = `
    {{.Name}} wants to say {{"blabla" | .Say}}
    {{.Name}} wants try again, {{call .Say "blabla"}}.`

    var h = &Human{"Tim"}

    t := template.Must(template.New("").Parse(letter))
    err := t.Execute(os.Stdout, h)
    if err != nil {
        log.Println("executing template:", err)
    }

}

see this code in play.golang.org

I thought that call calls functions/methods, but as it turned out we can do it just by .Method arg1 arg2. So what is function call intended for?

Answer 1

You need to use call if you want to call a function value.

To quote the docs (See under Functions):

Thus "call .X.Y 1 2" is, in Go notation, dot.X.Y(1, 2) where Y is a func-valued field, map entry, or the like.

In this example X could look like this:

type X struct {
    Y func(a int, b int) int
}