Buffalo Golang

The Golang web app framework, Buffalo, has a very good templating system called Plush. It adds some nice features to the standard library templating specific to web applications such as partials and local context. It’s pretty intuitive if you’re coming from Rails.

While the default setup makes rendering a template as a response to a request super easy, using rendered template content elsewhere isn’t so obvious.

Once you see it though, it’s pretty straightforward to render a template to a string within your action handler functions. Typically, we’d render a template like this:

func homeHandler(c buffalo.Context) error {
	return c.Render(200, r.HTML("index.html"))
}

Today I needed to return some HTML in a JSON resposne to a webhook to display some of our content within HelpScout for their dynamic app integration. Originally, I had a simple link to render which I did as:

render(200, r.JSON(
	struct {
		HTML string `json:"html"`
	}{
		HTML: fmt.Sprintf(`<a href="%s/users/%s">%s's profile</a>`, HOST, user.ID, user.FullName()),
	}),
)

This barely worked for this case, but it did work. Then we wanted to add more info and I wasn’t willing to write HTML within a Sprintf call. There are three steps to render an arbitrary template to a string:

• Allocate an io.Writer to hold the rendered template’s contents
• Render the template with a Renderer.
• Read the string from the Writer.

Here’s the code:

// allocate a buffer to render the template into
respBuf := &bytes.Buffer{}

// set any required values in the context (could be any `render.Data`)
c.Set("user", user)

// create the Renderer with the HTML method and call Render with the buffer and the necessary data
err = r.HTML("helpscout/sidebar.html", "layouts/zero.html").Render(respBuf, c.Data())
if err != nil {
	err = errors.WithStack(err)
	return err
}

// read the string out of the buffer (and in this case render it into a JSON response)
return c.Render(200, r.JSON(helpscoutResponse{HTML: respBuf.String()}))

That’s it. It’s pretty straightforward once you see it laid out. Hope this helps you (as I’m sure it will help me in 6 months).

– Chris