Web Atoms MVVM

Web Atoms MVVM Pattern Library

• Support for ViewModel
• Support for Commands
• Support for Message Broadcast/Subscriptions for communication between ViewModels
• Support for REST Service similar to Retro Fit
• Simple and Small Dependency Injection
• Example, Web Atoms MVVM Todo Sample

Installation

Dependency

Please add following Web Atoms to your Html page or Project.

Web Atoms

CDN in Production

<script 
src="//cdn.jsdelivr.net/npm/[email protected]/dist/web-atoms-mvvm.min.js">

NPM Package

npm install web-atoms-mvvm

Unit testing

For unit testing, please see
Web Atoms Unit

All Samples are in TypeScript

Sample REST Service

    var BaseService = WebAtoms.BaseService;

    @DIGlobal
    class BackendService extends BaseService{


        @Get("/task/{taskId}")
        getTask(
            @Path("taskId") taskId:number
        ): Promise<Task>{
            return null;
        }

        @Put("/task/{taskId}")
        saveTask(
            @Path("taskId") taskId: number, 
            @Body task:Task
        ):Promise<Task>{
            return null;
        }

        @Delete("/task/{taskId}")
        deleteTask(
            @Path("taskId") taskId: number
        ):Promise<any>{
            return null;
        }


        // support for CancelToken
        
        @Get("/tasks")
        getTasks(
            @Query("deleted" deleted: boolean,
            @Cancel cancel:CancelToken
        ):Promise<Array<Task>>{
            return null;
        }
        

    }

Sample View Model

    var AtomViewModel = WebAtoms.AtomViewModel;
    var AtomList = WebAtoms.AtomList;
    var AtomCommand = WebAtoms.AtomCommand;
    

    class Task{
        id: number;
        label: string;
        status: string;
    }

    class TaskViewModelErrors extends AtomErrors{

        @bindableProperty
        label: string;

        @bindableProperty
        status: string;
    }

    class TaskViewModel extends AtomViewModel{
        
        @bindableProperty
        list:AtomList<Task>;

        @bindableProperty
        newItem:Task;

        @bindableProperty
        selectedItem: Task;

        addCommand: AtomCommand<any>;
        removeCommand: AtomCommand<Task>

        backendService: BackendService;

        errors:TaskViewModelErrors;

        constructor(){
            this.list = new AtomList<Task>();
            this.newItem = new Task();
            this.addCommand = new AtomCommand(a => onAddCommand());
            this.removeCommand = new AtomCommand(task => 
                onRemoveCommand(task);)

            // simple dependency injection !!!
            this.backendService = WebAtoms.DI.resolve(BackendService);


            // setup validation
            this.errors = new TaskViewModelErrors();

            this.addValidation(
                () => this.errors.label = this.newItem.label ? "" : "Task cannot be empty",
                () => this.errors.status = this.newItem.status ? "" : "Status cannot be empty"
            );
        }

        async init():Promise<any>{
            var results = await this.backendService.getTasks(false);
            this.list.addAll(results);
        }

        onPropertyChanged(name:string){
            // called when any property of this viewmodel
            // is modified anywhere
        }

        async addCommand():Promise<any>{

            var windowService = WebAtoms.DI.resolve(WindowService);
            if(this.errors.hasErrors()){
                windowService.alert("Please complete all required fields");
                return;
            }

            this.newItem = 
                await this.backendService.saveTask(this.newItem);

            this.list.add(this.newItem);
            this.newItem = new Task();

        }

        async removeCommand(task:Task):Promise<any>{

            await this.backendService.deleteTask(task.id);

            this.list.remove(task);
        }

    }

Sample HTML

        <div 
            atom-type="AtomApplication"
            atom-view-model="{ new TaskViewModel() }">
            <div>
                <input type="text" 
                    atom-value="$[viewModel.newItem.label]" 
                    placeholder="New Task"/>
                <button 
                        atom-type="AtomButton" 
                        atom-command="{$viewModel.addCommand}">Add Mew</button>
            </div>
                

            <div 
                    atom-type="AtomListBox"
                    atom-items="[$viewModel.list]">
                <div atom-template="itemTemplate">
                    <span atom-text="{$data.label}"></span>
                    <button 
                            atom-type="AtomDeleteButton"
                            atom-command="{$viewModel.removeCommand}"
                            atom-command-parameter="{$data}">Delete</button>
                </div>
            </div>            
        </div>

Sample Broadcast Listener

Let's assume, you have a Atom Component that displays notifications. And you have set atom-view-model to NotificationServiceViewModel

    class AtomNotification {

        static short(message: string, title: string = ""): AtomNotification {
            return new AtomNotification(message, title);
        }

        constructor(
            message: string, 
            title: string, 
            icon: string = null, 
            delay: number = 5000)
        {
            this.message = message;
            this.title = title;
            this.icon = icon || "";
            this.delay = delay || 5000;
        }

        message: string;
        title: string;

        // displayed on left side..
        icon: string;

        // maximum delay to be displayed
        @bindableProperty
        delay: number;

        timeout: number;

    }

    class NotificationServiceViewModel extends AtomViewModel {

        notifications: AtomList<AtomNotification>;

        removeCommand: AtomCommand<AtomNotification>;

        constructor() {
            super();

            this.notifications = new AtomList<AtomNotification>();

            this.removeCommand = new AtomCommand <AtomNotification>(n => this.onRemoveCommand(n));

        }

        @receive("ui-notification")
        uiNotification(channel:string, data: AtomNotification){
            this.onNotified(data);
        }

        async onRemoveCommand(n: AtomNotification): Promise<any> {
            this.notifications.remove(n);
            if (n.timeout) {
                clearTimeout(n.timeout);
            }
        }

        async onNotified(n: AtomNotification): Promise<any> {
            this.notifications.add(n);
            if (n.delay > 0) {
                this.updateTimer(n);
            }
        }

        // this will reduce delay by 1000 millseconds
        // you can bind `n.delay` to display "Closing in (n) seconds" etc 
        private updateTimer(n: AtomNotification): void {
            if (n.delay > 0) {
                n.delay = n.delay - 1000;
                setTimeout(() => this.updateTimer(n), 1000);
            } else {
                this.notifications.remove(n);
            }
        }

    }

Sample Notification UI

    <div 
         atom-type="AtomItemsControl"
         atom-view-model="{ new NotificationServiceViewModel() }"
         atom-items="{$viewModel.notifications}"
         style="position:absolute;top:0;left:0;"
         style-display="[$viewModel.notifications.length ? 'block' : 'none']"
         style-width="100%"
         style-height="100%">

        <div style="margin:200px;position:relative;opacity:0.5;background-color:aquamarine"
             atom-presenter="itemsPresenter">
             <div atom-template="itemTemplate">
                 <div>
                     <span atom-text="{$data.title}"></span>
                     <button 
                             atom-type="AtomButton"
                             atom-command-parameter="{$data}"
                             atom-command="{$viewModel.removeCommand}"
                             >Close</button>
                 </div>
                 <div atom-text="{$data.message}"></div>
                 <div atom-text="['Closing in (' + (($data.delay/1000)+1) + ') seconds.. ']"></div>
             </div>
        </div>

    </div>

Reference

AtomDisposable

    interface AtomDisposable{
        dispose();
    }

    // action f will be called on dispose
    class DisposableAction implements AtomDisposable{
        constructor(f:()=>void);
    }

Atom

    class Atom{

        // watch for change in property in target object
        // method will return subscription, you can call dispose to 
        // remove subscription to avoid memory leak
        static watch(target:any, property:string, f:()=>void) : AtomDisposable;

        static async delay(n:number, ct?:CancelToken):Promise<any>;
    }

AtomCommand

Although you can directly call viewModel methods into binding expressions, we recommend using AtomCommand, as command has busy property, which will be set to true when asynchronous Promise is still executing.

You can set enabled to false to disable any UI associated with it, AtomButton automatically binds to enabled property.

    class AtomCommand<T>{

        @bindableProperty
        enabled: boolean;

        @bindableProperty
        busy: boolean;

        constructor( action:(T) => any );
    }

AtomModel

    class AtomModel{

        // this will notify bindings to refresh the UI
        refresh(field:string);
    }

AtomViewModel

    class AtomViewModel extends AtomModel{
        constructor();
        async init();
        dispose();

        broadcast(message:string,data:any);

        addValidation(...f:(()=>any)[]);

        // you can register a disposable which will
        // be disposed when View Model will be disposed by the UI service
        registerDisposable(d:AtomDisposable);

        // called when any property of view model
        // is changed
        onPropertyChanged(name:string);


        // decorators for AtomViewModel

        // @receive(...string[]) sets up receiver for broadcast for given channels

        // @watch sets up watching and evaluating expressions when any of property gets modified

        // @validate sets up validation (same as addValidation)

    }

AtomDevice

    type AtomAction = (msg: string, data: any) => void;

    class AtomDevice{

        // only access static instance
        // never create an instance
        static instance:AtomDevice;

        broadcast(message:string, data:any);

        // method will return subscription
        // you must call subscription.dispose() to avoid memory leak
        subscribe(message:string, action:AtomAction ): AtomDisposable;

        // takes care of errors
        runAsync<T>(task:Promise<T>):Promise<any>;
    }

AtomList

    class AtomList<T>{
        add(item:T):number;
        addAll(items:Array<T>);
        insert(i: number, item: T);
        removeAt(i: number);
        remove(item: T| (t:T) => bool);
        clear();
        
        // refreshes binding
        refresh();        

        // watch for changes in events..
        // type: (add/remove)
        // returns AtomDisposable
        // you must call dispose on AtomDisposable to avoid
        // memory leak
        watch(f:(type:string, index:number)=>void): AtomDisposable;

    }

DI

    class DI{

        // this will resolve instance
        // by providing type
        // example,
        //
        //      @DIGlobal
        //      class BackendService{
        //          ....            
        //      }
        //
        //      var servie = WebAtoms.DI.resolve(BackendService);
        static resolve<T>(c:new () => T):T;


        // register a type in code instead of @DIGlobal
        // example,
        //
        //      WebAtoms.DI.register(BackendService, () => new BackendService()  );
        static register<T>(c:new ()=>T, factory: ()=> T);


        // manually override global instance, if you want to override factory, you can
        // call register method
        // example,
        //
        //      WebAtoms.DI.override(BackendService, new MockBackendService());
        // 
        static override<T>(c:new () => T, instance:T);

    }

Window Service

    @DIGlobal
    class WindowService{

        async confirm(msg:string, title?:string):Promise<boolean>

        async alert(msg:string, title?:string): Promise<boolean>

        async openWindow<T>( windowType: (string | new() => AtomWindow), viewModel?: AtomViewModel ): Promise<T>

    }

Web Atoms Custom Controls (Custom Components)

You can create sample component as shown below and it will generate JavaScript which you can use as custom control. As dividing html into smaller fragments is pain, instead, small individual components can be scattered around in folders for better management and component generator will generate single JavaScript which can be reused on pages.

Component supports style with css/less tags.

    <!-- declaration of custom control -->

    <div 
        class="task-list"
        atom-component="TaskList"
        atom-view-model="{ new TaskListViewModel() }">

        <style>
            .task-list {
                > div {
                    color: gray;
                }
            }
        </style>

        <div>
            <input atom-text="$[viewModel.newItem.label]">
            <button atom-event-click="{ => $viewModel.addTask() }"></button>
        </div>
        <div atom-type="AtomItemsControl" atom-items="[$viewModel.items]">
            <div>
                <span atom-text="{$data.label}"></span>
                <button 
                    atom-type="AtomDeleteButton"
                    atom-next="{ => $viewModel.deleteTask($data) }"></button>
            </div>
        </div>
    </div>

Component Generator

    node node_modules/web-atoms-mvvm/bin/component-generator.js <source-folder>

    Example,
    node node_modules/web-atoms-mvvm/bin/component-generator.js app

waconfig.json

Component generator will lookup waconfig.json and will generate files accordingly. Sample waconfig.json

    {
        "srcFolder": "src/views",
        "outFile": "build/views.js",
        "namespace": ".. (namespace is optional) .."
    }

This will generate component.js for all html files app folder.

Usage

Once component is generated, you can include generated javascript file and create control in your main page as shown below.

    <!-- You can now create instance of TaskList on the main page -->
    <!-- as shown below -->

    <div atom-type="TaskList">
    </div>

Component Generator Task Example

Following is an example of how to add custom component generator task in VS Code.

    {
        "taskName": "Component Compiler",
        "command": "node",
        "isBackground": true,
        "presentation": {
            "echo": true,
            "reveal": "always",
            "focus": false,
            "panel": "dedicated"
        },
        "args": [
            "node_modules/web-atoms-mvvm/bin/component-generator.js",
            "app"
        ],
        "problemMatcher":{
            "owner": "cc",
            "fileLocation": ["relative", "${workspaceFolder}"],
            "pattern": {
                "regexp": "^([^\\(].*)\\((\\d+,\\d+)\\):\\s+(error|warning|info)\\s+(TS\\d+)\\s*:\\s*(.*)$",
                "file": 1,
                "location": 2,
                "severity": 3,
                "code": 4,
                "message": 5
            },
            "background": {
                
                "activeOnStart": true,
                "beginsPattern": "^\\s*\\d{1,2}:\\d{1,2}:\\d{1,2}(?: AM| PM)? - File change detected\\. Starting incremental compilation\\.\\.\\.",
                "endsPattern": "^\\s*\\d{1,2}:\\d{1,2}:\\d{1,2}(?: AM| PM)? - Compilation complete\\. Watching for file changes\\."
            }
        }
    }