[Schematics] 1. Copy and Manipulate Template

1. Create a src/my-component/files/src/app directory to hold your templates.

mkdir -p src/my-component/files/src/app

2. Create an app.component.ts file in src/my-component/files/src/app and put the following code in it:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  name = '<%= name %>';
}

The <%= name %> variable is an option you’ll pass in when running this Schematic. Create an app.component.html file with some HTML that reads the name variable.

3.  Add template as well:

<div style="text-align:center">
  <h1>
   Hello, {{ name }}
  </h1>
</div>

<router-outlet></router-outlet>

4. Now what we want is let user to give the 'name' thought prompt, In order to define the name prompt, create a schema.json file in the src/my-component directory.

{
  "$schema": "http://json-schema.org/schema",
  "id": "SchematicsMyComponent",
  "title": "My Component Schema",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "Your Name",
      "x-prompt": "What is your name?"
    }
  },
  "required": ["name"]
}

Then update src/collection.json to reference this file in a schema property.

{
  "$schema": "../node_modules/@angular-devkit/schematics/collection-schema.json",
  "schematics": {
    "my-component": {
      "description": "A blank schematic.",
      "factory": "./my-component/index#myComponent",
      "schema": "./my-component/schema.json"
    }
  }
}

5. Then update src/my-component/index.ts so you can get your generated project’s path, and copy templates.

import {
  apply,
  MergeStrategy,
  mergeWith,
  move,
  Rule,
  SchematicContext,
  template,
  Tree,
  url,
  FileEnty,
  forEach
} from '@angular-devkit/schematics';
import { join, normalize } from 'path';
import { getWorkspace } from '@schematics/angular/utility/config';

export function setupOptions(host: Tree, options: any): Tree {
  const workspace = getWorkspace(host);
  if (!options.project) {
    options.project = Object.keys(workspace.projects)[0];
  }
  const project = workspace.projects[options.project];

  options.path = join(normalize(project.root), 'src');
  return host;
}

export function myComponent(_options: any): Rule {
  return (tree: Tree, _context: SchematicContext) => {
    setupOptions(tree, _options);

    const movePath = normalize(_options.path + '/');
    const templateSource = apply(url('./files/src'), [
      template({..._options}),
      move(movePath),
      // fix for https://github.com/angular/angular-cli/issues/11337
      forEach((fileEntry: FileEntry) => {
        if (tree.exists(fileEntry.path)) {
          tree.overwrite(fileEntry.path, fileEntry.content);
        }
        return fileEntry;
      }),
    ]);
    const rule = mergeWith(templateSource, MergeStrategy.Overwrite);
    return rule(tree, _context);
  };
}

We can use this as a template when we want to add some template into the schematics.

6. Test with real application:

ng new my-test-app --routing --style css
cd my-test-app
npm link ../my-component
ng g my-component:my-component

When I tried this, it prompted me:

$ ng g my-component:my-component
? What is your name? Matt
UPDATE src/app/app.component.html (109 bytes)
UPDATE src/app/app.component.ts (207 bytes)

7. Support for ng add with Angular CLI:

A slick feature of Angular CLI is its ng add command. You can use it to invoke schematics and add features like PWA support and Angular Material to your projects. For example:

ng add @angular/pwa
ng add @angular/material

You can support for ng add $your-schematic too! Open my-component/src/collection.json and add a new ng-add schematic.

{
  "$schema": "../node_modules/@angular-devkit/schematics/collection-schema.json",
  "schematics": {
    "my-component": {
      "description": "A blank schematic.",
      "factory": "./my-component/index#myComponent",
      "schema": "./my-component/schema.json"
    },
    "ng-add": {
      "factory": "./ng-add/index",
      "description": "Add schematic",
      "schema": "./my-component/schema.json"
    }
  }
}

Create src/ng-add/index.ts and add the code necessary for it to invoke the my-component schematic.

import { chain, Rule, schematic, SchematicContext, Tree, } from '@angular-devkit/schematics';

export default function (options: any): Rule {
  return (host: Tree, context: SchematicContext) => {
    return chain([
      schematic('my-component', options)
    ])(host, context);
  };
}

After build, link to project, then you can run:

ng add my-component

Source