How to create a modal popup that is compatible with Angular 4

Question

I want to be able to create a popup window which will load a certain Angular 4 component of mine when a radio button is selected.

It seems that the methods listed in the answers to this question are only compatible with Angular 2.

I am not sure where to begin and would appreciate any help!

Answer 1

The accepted answer adds a large dependency to swat a fly. Modal (and modeless) dialogs are largely the result of a CSS class or two. Try this "rename..." example:

1) Write the parent and child-modal as if the child wasn't modal at all, but just an inline form with *ngIf attached.

Parent HTML that uses <my-modal> child:

<div>
    A div for {{name}}.
    <button type="button" (click)="showModal()">Rename</button>
    <my-modal *ngIf="showIt" [oldname]="name" (close)="closeModal($event)"></my-modal>
</div>

Parent class. The @Component decorator omitted for brevity. (The name property belongs to the parent class and would exist even if we didn't have a form to alter it.)

export class AppComponent {
    name = "old name";

    showIt = false;
    showModal() {
        this.showIt = true;
    }
    closeModal(newName: string) {
        this.showIt = false;
        if (newName) this.name = newName;
    }

}

Child to-be-modal component. @Component decorator and imports again omitted.

export class MyModalComponent {
    @Input() oldname = "";
    @Output() close = new EventEmitter<string>();
    newname = "";

    ngOnInit() {
        // copy all inputs to avoid polluting them
        this.newname = this.oldname; 
    }

    ok() {
        this.close.emit(this.newname);
    }

    cancel() {
        this.close.emit(null);
    }
}

Child HTML before modal-izing it.

<div>
    Rename {{oldname}}
    <input type="text" (change)="newname = $event.target.value;" />
    <button type="button" (click)="ok()">OK</button>
    <button type="button" (click)="cancel()">Cancel</button>
</div>

2) Here's the CSS for child, but it can be placed in a global stylesheet for re-use throughout your app. It's a single class called modal and is intended for a <div> element.

.modal {
    /* detach from rest of the document */
    position: fixed;

    /* center */
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);

    /* ensure in front of rest of page -- increase as needed */
    z-index: 1001;

    /* visual illusion of being in front -- alter to taste */
    box-shadow: rgba(0,0,0,0.4) 10px 10px 4px;

    /* visual illusion of being a solid object -- alter to taste */
    background-color: lightblue;
    border: 5px solid darkblue;

    /* visual preference of don't crowd the contents -- alter to taste */
    padding: 10px;
}

But the modal CSS class won't prevent interacting with the page underneath it. (So it technically creates a modeless dialog.) So we place an overlay underneath the modal to absorb and ignore mouse activity. overlay is also intended for a <div> element.

.overlay {
    /* detach from document */
    position: fixed;

    /* ensure in front of rest of page except modal */
    z-index: 1000;

    /* fill screen to catch mice */
    top: 0;
    left: 0;
    width: 9999px;
    height: 9999px;

    /* dim screen 20% -- alter to taste */
    opacity: 0.2;
    background-color: black;
}

3) Use the modal and overlay in the child HTML.

<div class="modal">
    Rename {{oldname}}
    <input type="text" (change)="newname = $event.target.value;" />
    <button type="button" (click)="ok()">OK</button>
    <button type="button" (click)="cancel()">Cancel</button>
</div>
<div class="overlay"></div>

And that's it. Basically 2 CSS classes and you can make any component a modal. In fact you can show a component in-line or as a modal at run-time just by altering the existance of the CSS class with ngClass or [class.modal]="showAsModalBoolean".

You can alter this so the child controls the show/hide logic. Move the *ngIf, showIt, and show() function into the child. In the parent add @ViewChild(MyModalComponent) renameModal: MyModalComponent; and then the parent can imperatively call this.renameModal.show(this.name); and re-wire initialization and containing divs as needed.

The child-modal can return info to a parent's function as shown above, or the child's show() method could instead accept a callback or return a Promise, as per taste.

Two things to know:

this.renameModal.show(..); won't work if there's an *ngIf on <my-modal> because it won't exist to expose the function to begin with. *ngIf removes the whole component, show() function and all, so use [hidden] instead if you need this for some reason.

Modals-on-modals will have z-index issues since they all share the same z-index. This can be solved with [style.z-index]="calculatedValue" or similar.