How to organize alert messages in DCG html?

Help!
1

I store alert messages in sessions and want to show them once after an action, for example ‘Topic is created successfully’. In DCG I’m trying to get a message and insert a div into html//1, but it doesn’t work. What am I doing wrong?

courses_body -->
	{
		functions:get_session_message(create_course_message, Message),
		( \=(Message, '')
		-> MessageDiv = [div(class('alert alert-success'), Message)]
		)
	},
	html([
		div(class(row),
			div(class('col-sm-12'), [
				\MessageDiv,
				h1('Список курсов'),
				a(href('/admin/courses/add'), 
					button([type("button"),class("btn btn-success")], 'Добавить курс')
				)
			])
		)	
	]).
2

If functions:get_session_message/2 fails or Message unifies with '' then the whole production courses_body//0 fails. Then you should handle this case where you call it, or just add the else branch:

    {
		(  functions:get_session_message(create_course_message, Message),
		   Message \= ''
		-> MessageDiv = [div(class('alert alert-success'), Message)]
        ;  MessageDiv=''
		)
	},

The outcome is a bit verbose when compared to imperative/functional languages… but overall, I’m not sure about the ‘temporal scope’ of your code. Maybe the whole problem is to lift the message in Javascript, or setup an AJAX roundtrip…

3

Well, it would be good to use JS and I was wondering is it possible to use a JS framework (ex. vue.js) with Prolog? I know how to launch JS frameworks via Apache or nginx, but how to connect it with web Prolog?

4

There are many variations about Javascript <-> SWI-Prolog interaction, a practical example and most simple example is WebChat, that shows websockets at work.

SWISH is a showcase for Pengines, but there the application is complex and hides the basic architecture…

I have never used VueJS - but have some experience with React (and React Native+Expo), Node+ExpressJS, Svelte.

I must say that I’m not a big fan of these, currently I prefer plain HTML5, eventually with jQueryUI.
Continuous improvements in JS (and PHP) have made the old LAMP architecture a good fit for my professional duties…

Maybe today will try to port to websockets the CLP(FD) visualization proposed by M.Triska.