YAGA - leaflet-ng2

YAGA leaflet-ng2 is a granular implementation of the popular Leaflet framework into the model view view controller (MVVC) of Angular.io. It provides a directive for every Leaflet class that belongs to the user interface by inheriting the original Leaflet class and enhancing it with the decorators of Angular and glue-code. With this approach the directives are still extensible and it is possible to write the structure of an app in a descriptive way in a well known markup language, HTML5. This is why you mainly need HTML skills for creating a template based geo-app with leaflet-ng2.

It is easy to enhance this library with one’s own Angular modules, because of its modular structure. It is even possible to use the already existing Leaflet plugins on top, because the implementation also detects changes that were made in Leaflet and bind them to Angular’s data model.

The YAGA Development-Team gives a great importance to tests, test-coverage, documentation, examples and getting started templates.

How to use

First you have to install this library from npm:

npm install --save @yaga/leaflet-ng2

This module works like a normal Angular 2 module. You should do something like that:

import { YagaModule, OSM_TILE_LAYER_URL }   from '@yaga/leaflet-ng2';
import { Component, NgModule, PlatformRef } from '@angular/core';
import { BrowserModule }                    from '@angular/platform-browser';
import { platformBrowserDynamic }           from '@angular/platform-browser-dynamic';

const platform: PlatformRef = platformBrowserDynamic();

@Component({
    selector: 'app',
    template: `<yaga-map><yaga-tile-layer [(url)]="tileLayerUrl"></yaga-tile-layer></yaga-map>`
})
export class AppComponent {
    // Your logic here, like:
    public tileLayerUrl: string = OSM_TILE_LAYER_URL;
}

@NgModule({
    bootstrap:    [ AppComponent ],
    declarations: [ AppComponent ],
    imports:      [ BrowserModule, YagaModule ]
})
export class AppModule { }

document.addEventListener('DOMContentLoaded', () => {
    platform.bootstrapModule(AppModule);
});

Do not forget to import the leaflet css!

After that you should be able to use the following directives or components:

• yaga-map This must be the root component!
• yaga-attribution-control
• yaga-circle
• yaga-circle-marker
• yaga-div-icon
• yaga-feature-group
• yaga-geojson
• yaga-icon
• yaga-image-overlay
• yaga-layer-group
• yaga-layers-control with [yaga-base-layer] and [yaga-overlay-layer]
• yaga-marker
• yaga-polygon
• yaga-polyline
• yaga-popup
• yaga-rectangle
• yaga-scale-control
• yaga-tile-layer
• yaga-tooltip
• yaga-zoom-control

For further information look at the api documentation or the examples.

Use in combination with a CLI

For developing we recommend to use a command-line-interface like angular-cli for web-applications or ionic for smartdevice-like apps.

You can also check out our ionic-starter templates on our GitHub account

Start a project with Angular CLI

You have to perform the followings steps to start a project with the angular-cli:

# Install the angular-cli to your system
npm install -g angular-cli
# Create a app with the angular-cli
ng new my-yaga-app
# Switch into the created project directory
cd my-yaga-app
# Install @yaga/leaflet-ng2 as project dependency
npm install --save @yaga/leaflet-ng2

Import the YAGA module into your app in app.module.ts:

// other imports...
import { YagaModule } from '@yaga/leaflet-ng2';

// ...

@NgModule({
  imports: [
    // other...
    YagaModule,
  ],
  // some other properties...
)
export class AppModule { }

Start a project with Ionic CLI

You have to perform the followings steps to start a project with the ionic-cli:

# Install the ionic-cli to your system
npm install -g ionic
# Create a app with the ionic-cli (select a template unteractive)
ionic start my-yaga-app
# Switch into the created project directory
cd my-yaga-app
# Install @yaga/leaflet-ng2 as project dependency
npm install --save @yaga/leaflet-ng2

Import the YAGA module into your app in app.module.ts:

// other imports...
import { YagaModule } from '@yaga/leaflet-ng2';

// ...

@NgModule({
  imports: [
    // other...
    YagaModule,
  ],
  // some other properties...
)
export class AppModule { }

Use standard Leaflet plugins

You are able to integrate other Leaflet plugins (not prepared for the use with Angular) by importing the map directive into your parent directive like this:

@Component({
    selector: 'app',
    template: `<yaga-map><!-- ... --></yaga-map>`
})
export class AppComponent implements AfterViewInit {
    @ViewChild(MapComponent) private mapComponent: MapComponent;
    public ngAfterViewInit(): void {
        const myFancyLeafletPlugin = (L as any).myFancyLeafletPlugin({ /* ... */ });
        this.mapComponent.addSomething(myFancyLeafletPlugin);
    }
}

For further information, take a look at the according issue on GitHub

Write as a YAGA Module

To write an existing extension as a YAGA directive is made as easy as possible. Your Leaflet-Plugin of choice should already have a TypeScript type-definition. At first take a look which Leaflet base-class your Leaflet-Plugin of choice implements. Than copy the implementation and software-tests of the according base-class in this repository and enhance it accordingly to the given schema.

List of providers

• MapProvider - Inject this provider for classes that have to interact with the Map class and not with a LayerGroup. Controls typically use the MapProvider
• LayerGroupProvider - Inject this provider for classes that implements Layers. Note that the Map also provides a LayerGroupProvider, but it is @Host and you are not able to request a higher one in the dependency-chain.
• LayerProvider - Every class that implements Layer should have a LayerProvider to give for example Popups the possibility to get access to this.
• MarkerProvider - Use this to add Icons.

Example

Every class that extends a layer in Leaflet must provide a LayerProvider. Layers in Leaflet needs typically a Map or LayerGroup to have the possibility to add it to that (layer.addTo(MapOrLayerGroup)). So every instance of a LayerGroup must provide a LayerGroupProvider.

With the information of the above mentioned architecture, you have to implement a LayerGroupDirective (which is extended from Leaflet's LayerGroup class, which is - in turn - extended from Leaflet's Layer) like this:

import { Directive, SkipSelf } from '@angular/core';
import { LayerGroupProvider, LayerProvider } from '@yaga/leaflet-ng2';
import { FeatureGroup } from 'leaflet';

@Directive({
    providers: [ LayerGroupProvider, LayerProvider ], // Provide a new Layer and LayerGroup
    selector: 'yaga-feature-group',
})
export class FeatureGroupDirective extends FeatureGroup {

    constructor(
        @SkipSelf() parentLayerGroupProvider: LayerGroupProvider, // Use SkipSelf to access the parent provider
        layerGroupProvider: LayerGroupProvider, // Import new Provider to reference this class
        layerProvider: LayerProvider, // Import new Provider to reference this class
    ) {
        super();

        layerProvider.ref = this; // Reference this class to created provider
        layerGroupProvider.ref = this; // Reference this class to created provider

        this.addTo(parentLayerGroupProvider.ref); // Add it to parent LayerGroup (which can also be a map)
    }
}

Scripts Tasks

Scripts registered in package.json:

• init: Install all stuff needed for development (Typings, libs etc.)
• clean: Remove the stuff from init-task
• reinit: Call clean and init
• transpile: Transpile TypeScript Code to JavaScript
• lint: Use the linter for TypeScript Code
• test: Run software- and coverage-tests in node.
• browser-test: Build the tests for the browser.
• build-examples: Build the examples.
• doc: Build the API documentation.

Every command is also available as dockerized version, by prefixing docker: (ex.: docker:lint)

License

This library is released under the ISC License.

Links

• YAGA-Website
• Project-Website
• Unit-Tests
• Test-Coverage
• API-Documentation
• GitHub
• NPM
• Workshop with Ionic 2
• Video-Playlist (YouTube)