Rendering html/template (Beginner)

[danny (Daniel Osineye)]

I need help on rendering html templates on an existing page.

I’ll appreciate a sample code.
Cheers.

[elithrar (Matt Silverlock)]

Please run through this tutorial: https://golang.org/doc/articles/wiki/#tmp_6 and then read http://jan.newmarch.name/go/template/chapter-template.html

If you get stuck, post your code and I’m sure we can help.

[danny (Daniel Osineye)]

Okay, thanks.
The issue is actually passing in new variables to an html template.

I’ll revert when I have to.

Cheers.

[elithrar (Matt Silverlock)]

Can you show what (the code) you have tried so far?

[danny (Daniel Osineye)]

I haven’t tried any yet, I can only render static html templates like this

t, _ = t.parseFiles(“learn.html”)
t.Execute(w, nil)

I understand this…

But, I’m still trying to fifure out how to pass variables like this

{{ .value}}

The book you shared is helping.

[geosoft1 (George Calianu)]

first, you must have {{.Value}} not {{.value}} in your template file. also, you must create a struct which contain Value field in your main go file and a properly variable

type Page struct {
    Value string
}
var p Page

in your main function you can use something like this to read template

t = template.New("templ")
t.ParseGlob("*.html")

then in the place you want to render template use

t.ExecuteTemplate(w, "learn.html", p)

[danny (Daniel Osineye)]

Thanks geosoft… I got an error from “value” and changed to Value.

How can this code work. From the first page, I want the post(from the form) method to render a new page. Code compiles but the conval.html is not rendered.

Same code in the screenshot

Is this a wrong practice?

func serveComment(writer http.ResponseWriter, request *http.Request){
if request.Method == “GET”{
t, _ := template.ParseFiles(“comment.html”)
t.Execute(writer, nil)
}else{
request.ParseForm()
// render
u := currentUser.Nick
ucomment := request.FormValue(“talk”)
// commTime := time.Now().String()

    dude := Comment{
        Person: Person{
            Nick: u,
        },
        value: ucomment,
    }
    t, err := template.ParseFiles("comval.html")
    if err != nil{
        log.Fatal(err)
    }

    err = t.Execute(writer, dude)
    if err != nil{
        log.Fatal(err)
    }
}

}

[coleman (Coleman McFarland)]

You are basically on the right track with templates. I have another suggestion, though.

Since you are inside of a function that does HTTP handling, it is not a good idea to do log.Fatal(..), in my opinion. Fatal will exit your program, which is not what you want. See: https://golang.org/pkg/log/#Fatal

Instead, use the Error function from the http package. See the documentation: https://golang.org/pkg/net/http/#Error

So, do this instead

    err = t.Execute(writer, dude)
    if err != nil{
        http.Error(writer, "Could not render template.", 500)
        return  // required to stop further writes to response
    }

Finally, it is easier to read your code if it is in Markdown format, instead of screenshots.

[geosoft1 (George Calianu)]

comval.html is not rendered more probably because has some syntax errors.

on the other hand @coleman has right about log.Fatal usage but in your particular case log.Fatal can be used because without a valid template your code wont work properly. so i think that another good practice can be putting the template parsing somewhere in the main function not in the http handler.

[elithrar (Matt Silverlock)]

@coleman

So, do this instead

err = t.Execute(writer, dude)
if err != nil {
    http.Error(writer, err.Error(), 500)
    return
}

You missed a naked return (I’ve added it) If you miss that, your handler continues, potentially trying to write to the ResponseWriter again and corrupting it.

[elithrar (Matt Silverlock)]

@danny

But, I’m still trying to fifure out how to pass variables like this

{{ .value}}

Run through the entire tutorial I linked: Writing Web Applications - The Go Programming Language

It shows how to pass data to a template.

<h1>Editing {{.Title}}</h1>

<form action="/save/{{.Title}}" method="POST">
<div><textarea name="body" rows="20" cols="80">{{printf "%s" .Body}}</textarea></div>
<div><input type="submit" value="Save"></div>
</form>

(I’ve simplified the code below to make it even clearer)

func editHandler(w http.ResponseWriter, r *http.Request) {
    title := r.PostForm("title")
    p := &Page{Title: title}
    t, err := template.ParseFiles("edit.html")
    if err != nil {
        // Only expose your errors publicly in development 
        http.Error(w, err.Error(), 500)
        return
    }
    t.Execute(w, p)
}

[danny (Daniel Osineye)]

Thanks a lot, I have been taking my time to look at your solutions and they have been helpful. I’ll always refer to them, when need be.

Cheers.