Add Custom Render Support via Reply

[jeevatkm]

Add custom render support via Reply. So that aah user can implement interface aah.Render and supply it as custom render.

Classic real time usage is JSON API response - https://github.com/google/jsonapi.

Samples

Sample 1

// CustomRender implements the interface `aah.Render`.
type CustomRender struct {
    // ... your fields goes here
}

func (cr *CustomRender) Render(w io.Writer) error {
    // implement your rendering
    fmt.Fprint(w, "This is custom render struct")
    return nil
}

// Using it via Reply()
Reply().ContentType(jsonapi.MediaType).Render(&CustomRender{
    // your fields initialize goes here
})

Sample 2

Reply().ContentType(jsonapi.MediaType).
	Render(aah.RenderFunc(func(w io.Writer) error {
		// implement your rendering
		fmt.Fprint(w, "This is custom render func")
		return nil
	}))

[jeevatkm]

It's done :)

[AugustHell]

Cant get custom rendering to work for me

Hi, first of all, coding in php for almost 20 years, I'm pretty new to go (since a few months), but I'm having some experience in c and c# therefore go looks familiar to me.
I really like the coding style of aah and seriously trying it out since some days to see if I can get used to it and it meets my needs.

One of them is to have some kind of web components in my html templates. As our web design is made using the pinegrow web editor, I need to have a way to replace blocks with representing default content in the layout (always full pages, content of the block may be just an image of the output) with dynamic content of the database in template(s) - best way each block gets his own template.

Simple Example:
Layout:

<% block "content" %><img src="PresentationOfAProductDetail.jpg"><% end %>
</body></html>

Template:
<% define "content" %><div>picture and data of selected product</div><% end %>

This I can do with go html/template, but I don't find a way to do it with aah :(

First of all I expected Reply().HTMLlf(layout,template,data) would do it, but I don't know why the template isn't overriding the default of the layout.

Now I'm trying to build a custom render method, but yet the both base examples don't work:

package controllers

import (
	"fmt"
	"io"

	"aahframework.org/aah.v0"
)

// FastController struct application controller
type FastController struct {
	*aah.Context
}

// CustomRender aka interface `aah.Render`.
type CustomRender struct {
	// ... your fields goes here
}

// Render test
func (cr *CustomRender) Render(w io.Writer) error {
	// implement your rendering
	fmt.Fprint(w, "This is custom render struct")
	return nil
}

// Index method is application home page.
func (a *FastController) Index() {
	a.Reply().Render(&CustomRender{})
}

Internal Server Error:
interface conversion: aah.Render is *controllers.CustomRender, not *aah.HTML

RenderFunc:

package controllers

import (
	"fmt"
	"io"

	"aahframework.org/aah.v0"
)

// FastController struct application controller
type FastController struct {
	*aah.Context
}
// Index method is application home page.
func (a *FastController) Index() {

	// Using it via Reply()
	a.Reply().ContentType("text/html").Render(aah.RenderFunc(func(w io.Writer) error {
		// implement your rendering
		fmt.Fprint(w, "This is custom render func")
		return nil
	}))

}

Internal Server Error:
interface conversion: aah.Render is aah.RenderFunc, not *aah.HTML

$ go version
go version go1.9.4 windows/amd64

I've tried some things to get this conversion right, but got no success. Good chance I don't know yet, how to do it right.

[jeevatkm]

@AugustHell Thank you for using aah for your project. I'm glad to hear your appreciation.

Feel free to reach out on Gitter or here for any assistance with aah.

---

aah go view engine is enhanced features with default go template engine. So it has all the capabilities 😄

Let's get to your questions.

First you might have a read the aah views directory structure. Just give you a high level tour-

• Each Controller would have sub-directory under directory pages For e.g. Controller named FastController
• And Each Controller Action would have view template file. For e.g.: Action named Index

Now view template path is views/pages/fast/index.html

Next move on to Layout, if you take a closer look at layout master.html, you will see a line {{ template "body" . -}} and if you look at index.html you will see {{ define "body" -}}. In your example you have called this as content; I called that as body. It same as block keyword but with more options. Of course if you would like, you can use block too.

Next move on to Rendering-

• When you call Reply().HTML(data) from action FastController.Index - aah knows and it would render views/pages/fast/index.html with views/layouts/master.html
• When you call Reply().HTMLl("mylayout1.html", data) from action FastController.Index - aah knows and it would render views/pages/fast/index.html with views/layouts/mylayout1.html
• So as other methods Reply().HTML* gives your a control over layout, template file, etc.

I hope I have describe it alright. Bottomline, you can use all capabilities of go template engine with aah. If you see a trouble, that's where aah have to improve. please let me know, I would take care.

---

Regarding custom render, this error interface conversion: aah.Render is *controllers.CustomRender, not *aah.HTML smells. I will check and get back to you.

---

Thanks again for using aah.

[jeevatkm]

@AugustHell Thanks finding a bug #174, I have fixed it. Made v0.10.1 release. Please update aah at your end. You're good to go 👍

[AugustHell]

Thank you very much for your quick detailed reply and the aah update!

I understand the part of the layout and page rendering. Only, it doesn't work like I'd expect it. Maybe another quirk?

I'm using block instead of template, cause I like to have default content in the layout in place, that should be replaced by the controller with dynamic content on runtime.
The goal is, that web design is decoupled from the programming part in order to view and edit the layout "master.html" just from file without running a go server.

That could be done with template too, it's just a line more, but neither way is working if you look at this example:

layouts/master.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Block Test</title>
  </head>
  <body>
    <% template "body" . %>
    <% define "body" -%>
    <h1>Welcome to the Block Test</h1>
    <% end %>

    <section name="footer">
      <% block "footer" . %>
      <p><i>(served by master layout)</i></p>
      <% end %>
    </section>
  </body>
</html>

pages/app/index.html

<% define "body" %>
  <h1><% .Greet.Message %></h1>
<% end %>
<% define "footer" -%>
  <p><i>(served by app index controller)</i></p>
<%- end %>

app/controllers/app.go

package controllers

import (
	"aahframework.org/aah.v0"
	"athell.com/xhimport/v007fasttpl/app/models"
)

// AppController struct application controller
type AppController struct {
	*aah.Context
}

// Index method is application home page.
func (a *AppController) Index() {
	data := aah.Data{
		"Greet": models.Greet{
			Message: "Welcome to aah framework - Web Application",
		},
	}
	a.Reply().Ok().HTML(data)
}

If I run this, neither the body nor the footer default content is replaced, so nothing of pages/app/index.html is in the output.
Same result with
a.Reply().Ok().HTMLlf("master.html", "index.html", data)

Output:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Block Test</title>
  </head>
  <body>
    <h1>Welcome to the Block Test</h1>
    <section name="footer">
     <p><i>(served by master layout)</i></p>
    </section>
  </body>
</html>

BTW, highly welcomed would be, if there is a replay function that handles multiple "pages" like several blocks on a page

blocks := []string{
	"menu.html",
	"body.html",
	"links.html",
	"footer.html",
}
a.Reply().Ok().HTMLlf("master.html", blocks, data)

Another neat way would be if it is plugable, like in erlang/elixirs plug:
a.Replay().Ok().HTMLlf("master.html","menu.html",nil).HTMLf("body.html",data).HTMLf("footer.html",nil)

[jeevatkm]

@AugustHell I understand your goal (generally it should be 😄). I'm wondering why block is not working. I will check and get back to you.

Thanks for the suggestion on reply design. First I would like to understand how erlang/elixirs works then I could think on design. (Added note on Roadmap)