Go - Web application 3

Displaying dynamic data

func (app *application) snippetView(w http.ResponseWriter, r *http.Request) {
    id, err := strconv.Atoi(r.PathValue("id"))
    if err != nil || id < 1 {
        http.NotFound(w, r)
        return
    }

    snippet, err := app.snippet.Get(id)
    if err != nil {
        if errors.Is(err, models.ErrNoRecord) {
            http.NotFound(w, r)
        } else {
            app.serverError(w, r, err)
        }
        return
    }

    // Initialize a slice containing the paths to the view.html file, 
    // plus the base layout and navigation partial that we made earlier.
    files := []string{
        "./ui/html/base.html",
        "./ui/html/partials/nav.html",
        "./ui/html/pages/view.html",
    }

    // Parse the template files.
    ts, err := template.ParseFiles(files...)
    if err != nil {
        app.serverError(w, r, err)
        return
    }

    // And then execute them. Notice how we are passing in the snippet 
    // data (a models.Snippet struct) as the final parameter.
    err = ts.ExecuteTemplate(w, "base", snippet)
    if err != nil {
        app.serverError(w, r, err)
    }
}

Any data that you pass as the final parameter to ts.ExecuteTemplate() is represented within your HTML templates by the . character (referred to as dot).

In this specific case, the underlying type of dot will be a models.Snippet struct. When the underlying type of dot is a struct, you can render (or yield) the value of any exported field in your templates by postfixing dot with the field name. So, because our models.Snippet struct has a Title field, we could yield the snippet title by writing {{.Title}} in our templates.

{{define "title"}}Snippet #{{.ID}}{{end}}

{{define "main"}}
    <div class="snippet">
        <div class="metadata">
            <strong>{{.Title}}</strong>
            <span>#{{.ID}}</span>
        </div>
        <pre><code>{{.Content}}</code></pre>
        <div class="metadata">
            <time>Created: {{.Created}}</time>
            <time>Expires: {{.Expires}}</time>
        </div>
    </div>
{{end}}