ng-brainstorm: content projection

What does "content" mean?

  1. DOM I control that gets "threaded" into the component's DOM at some location
  2. A template for content that I want the element to be able to render many times, at will
  3. DSL for configuration/inputs (<router><route ...><route ...></router>)
  4. Plain text to transform (<markdown>...</markdown>)

Custom Elements API for slots




















<template>
  <slot name="user">
    <p>Default content for the user</p>
  </slot>
  <slot name="address">
    <!-- no default content provided -->
  </slot>
</template>


<!-- and in the consumer -->

<some-element>
  <user-card slot="user"></user-card>
  <address slot="address">
    <p>Line 1</p>
    <p>Line 2</p>
  </address>
</some-element>

Thoughts, in no particular order

  • Explicit API - slots are always keyed by their name
    • This could get boilerplate-y
  • No obvious way to pass more than one element
  • Default content is interesting
  • Should have some way to mark a slot as "required"
  • Only solves case 1 above.

Angular Material: Data Table

A basic data table.

































<table mat-table [dataSource]="dataSource" class="mat-elevation-z8">

  <!--- Note that these columns can be defined in any order.
        The actual rendered columns are set as a property on the row definition" -->

  <!-- Position Column -->
  <ng-container matColumnDef="position">
    <th mat-header-cell *matHeaderCellDef> No. </th>
    <td mat-cell *matCellDef="let element"> {{element.position}} </td>
  </ng-container>

  <!-- Name Column -->
  <ng-container matColumnDef="name">
    <th mat-header-cell *matHeaderCellDef> Name </th>
    <td mat-cell *matCellDef="let element"> {{element.name}} </td>
  </ng-container>

  <!-- Weight Column -->
  <ng-container matColumnDef="weight">
    <th mat-header-cell *matHeaderCellDef> Weight </th>
    <td mat-cell *matCellDef="let element"> {{element.weight}} </td>
  </ng-container>

  <!-- Symbol Column -->
  <ng-container matColumnDef="symbol">
    <th mat-header-cell *matHeaderCellDef> Symbol </th>
    <td mat-cell *matCellDef="let element"> {{element.symbol}} </td>
  </ng-container>

  <tr mat-header-row *matHeaderRowDef="displayedColumns"></tr>
  <tr mat-row *matRowDef="let row; columns: displayedColumns;"></tr>
</table>

Very structured, and yet super hard to understand still.

A silly straw man:








<mat-table [dataSource]="dataSource">
  <mat-table-column>
      <th>No.</th>
      <td></td>
  </mat-table-column>
  
</mat-table>

Notes from Pawel

  • static content projection - <ng-content>
  • "slot" vs css-selector
    • based on custom elements v0 spec
    • slots used by VueJS, Svelte, etc.
  • need to differentiate between what can be projected, and wrapping the projected node if present





<mat-card>
  <mat-card-actions slot="actions">
    <button>Click me</button>
  </mat-card-actions>
</mat-card>



<div *ngFor="let user of users" slot="user">
</div>






<div *ngForSlot="user">
  <div class="wrapper">
    <ng-content></ng-content>
  </div>
</div>









<menu>
    <item></item>
     <item></item>
      <item></item>
      -----
       <item></item>
        <item></item>
</menu>





<div *ngFor="let item of data">
  <ng-content [content]="item"></ng-content>
  <*item></*item>
</div>

@Component({...})
class FooCmp {
  @Content('slotname', {multi: true})
  data: Content<?>[];
}
  • mental model
  • API to grab/insert
  • API to name things











<mat-card>
  
  <:header>text</:header>
  
  
  <:header>
      <span>Title</span>
      <span>Sub-title</span>
  </:header>
  
</mat-card>




<div *ngIf="expr">
  ...
</div>

template + context

@Template(
template: '{{name}}'
)
export interface Foo {
name: string;
}

template + context = content
``
var Foo = makeTemplate<IFoo>('{{name}}');

@Component({
…
})
export class Foo {
@Input('name') name: IFoo['name'],
}

render(Foo, {name: 'Alex'});

Observable<Foo>.map(data => render(Foo, data)) => Observable<Content>

<ng-template-outlet [template]="Foo" [context]="{name: …}">

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