Angular Drag & Drop Between Lists

Last week I shared steps to make a drag & drop application in Angular in just a few minutes. This is great for sorting items within a single list, but drag & drop is more exciting when used for interaction between elements. Today we’ll look at what it takes to extend last week’s project to include two lists that we can drag & drop between.

Code from the previous article is available here.

The first thing we’ll do is modify the todo-list component to have two lists. Modify todo-list-component.html to have a second cdkDropList element as shown in the code below. We also need to indicate that these lists are connected.

<h2>TODO</h2>
<div 
    cdkDropList 
    #todoList="cdkDropList"
    [cdkDropListData]="tasks"
    [cdkDropListConnectedTo]="[doneList]"
    class="example-list" 
    (cdkDropListDropped)="drop($event)">
    <div class="example-box" *ngFor="let task of tasks" cdkDrag>{{task}}</div>
</div>
<h2>COMPLETED</h2>
<div
    cdkDropList 
    #doneList="cdkDropList"
    [cdkDropListData]="completedTasks"
    [cdkDropListConnectedTo]="[todoList]"
    class="example-list" 
    (cdkDropListDropped)="drop($event)">
    <div class="example-box" *ngFor="let task of completedTasks" cdkDrag>{{task}}</div>
</div>

Now we need to make a pair of changes to todo-list.component.ts. First, we need to add the completedTasks collection referenced by our second list. We also need to modify the drop event handler to determine whether we’re rearranging a list or moving an item between lists.

import { Component, OnInit } from '@angular/core';
import {CdkDragDrop, moveItemInArray, transferArrayItem} from '@angular/cdk/drag-drop';

@Component({
  selector: 'app-todo-list',
  templateUrl: './todo-list.component.html',
  styleUrls: ['./todo-list.component.css']
})
export class TodoListComponent implements OnInit {
  tasks = [
    'Cleaning',
    'Gardening',
    'Shopping'
  ];
  completedTasks = [];

  constructor() { }

  ngOnInit(): void {
  }

  drop(event: CdkDragDrop<string[]>) {
    if (event.previousContainer === event.container) {
      moveItemInArray(
        event.container.data, 
        event.previousIndex, 
        event.currentIndex);
    } else {
      transferArrayItem(
        event.previousContainer.data,
        event.container.data,
        event.previousIndex,
        event.currentIndex);
    }
  }
}

That’s it–we’re done! Let’s run the application and see what happens.

$ ng serve --open

We can now rearrange items in the individual lists, as we could before, and move items between the two lists. Final code for this article is available on GitHub, here.

Feature image by Alexandra_Koch from Pixabay

E2E Angular Drag & Drop App in 5 Steps

Image by sachin_21 from Pixabay

Drag & drop is one of the best enhancements you can implement to give your app a modern feel and provide a great user experience, and Angular’s Component Dev Kit (CDK) makes it really easy to do. In this article, we’ll build a new Angular app from scratch using the Angular CLI and add a drag & drop todo list component.

Prereqs: Make sure you have the Angular CLI installed. You can test by running the command ng --version. If you need to install it, run the command npm install -g @angular/cli. (If you have problems installing on Linux, maybe this article can help!)

Step 1: Create a new app

Create a new app using the Angular CLI. We’ll also install the Angular CDK, and make sure it all works:

$ ng new my-app --defaults
$ cd my-app
$ npm install @angular/cdk
$ ng serve --open

Step 2: Import DragDropModule

In order to make use of Angular CDK’s drag & drop module, we need to import it. Open app.module.ts and import DragDropModule by making the following two edits:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppComponent } from './app.component';
import { DragDropModule } from '@angular/cdk/drag-drop';

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

Step 3: Add a new component

Now we’ll use the Angular CLI again to add a new component:

$ ng generate component todo-list

Next we need to modify the component to handle the drop event. We’ll also add some hard-coded test data to work with. Open todo-list.component.ts and make the following changes:

import { Component, OnInit } from '@angular/core';
import {CdkDragDrop, moveItemInArray} from '@angular/cdk/drag-drop';

@Component({
  selector: 'app-todo-list',
  templateUrl: './todo-list.component.html',
  styleUrls: ['./todo-list.component.css']
})
export class TodoListComponent implements OnInit {
  tasks = [
    'Cleaning',
    'Gardening',
    'Shopping'
  ];

  constructor() { }

  ngOnInit(): void {
  }

  drop(event: CdkDragDrop<string[]>) {
    moveItemInArray(this.tasks, event.previousIndex, event.currentIndex);
  }
}

We also need to modify the component HTML. Update the contents of todo-list.component.html to be the following:

<div cdkDropList class="example-list" (cdkDropListDropped)="drop($event)">
    <div class="example-box" *ngFor="let task of tasks" cdkDrag>{{task}}</div>
</div>

Step 4: Use the new component

At this point, we’re actually done adding the basic drag & drop functionality, so let’s use our new component. Replace the entire contents of app.component.html with this:

<app-todo-list></app-todo-list>

Now, head back out to your terminal, re-launch the app, and–voila!–you’ve got drag & drop!

$ ng serve --open

(Optional) Step 5: Make it pretty

Sure it’s functional, but it doesn’t look very good! Spruce it up by adding the following CSS to todo-list.component.css:

.example-list {
  width: 500px;
  max-width: 100%;
  border: solid 1px #ccc;
  min-height: 60px;
  display: block;
  background: white;
  border-radius: 4px;
  overflow: hidden;
}

.example-box {
  padding: 20px 10px;
  border-bottom: solid 1px #ccc;
  color: rgba(0, 0, 0, 0.87);
  display: flex;
  flex-direction: row;
  align-items: center;
  justify-content: space-between;
  box-sizing: border-box;
  cursor: move;
  background: white;
  font-size: 14px;
}

.cdk-drag-preview {
  box-sizing: border-box;
  border-radius: 4px;
  box-shadow: 0 5px 5px -3px rgba(0, 0, 0, 0.2),
              0 8px 10px 1px rgba(0, 0, 0, 0.14),
              0 3px 14px 2px rgba(0, 0, 0, 0.12);
}

.cdk-drag-placeholder {
  opacity: 0;
}

.cdk-drag-animating {
  transition: transform 250ms cubic-bezier(0, 0, 0.2, 1);
}

.example-box:last-child {
  border: none;
}

.example-list.cdk-drop-list-dragging .example-box:not(.cdk-drag-placeholder) {
  transition: transform 250ms cubic-bezier(0, 0, 0.2, 1);
}

Ah, that feels a little better!

Intro to Unit Testing In Angular With Karma & Jasmine

Ah, unit testing. One of my favorite subjects. I’ve been big on unit tests for what seems like more than a decade now, but I’ve never dipped my toes into the UI unit test pool! It’s been long enough, though. It’s time to learn!

So, I’m taking my first look at writing tests for an Angular application using Karma and Jasmine. I thought this tutorial at scotch.io was a great first read. It provides overviews of what Karma and Jasmine are, and walks you through the steps of creating an Anuglar application and adding tests from scratch using the Angular CLI, and that’s basically the foundation I’m working with today.

In this article, I’m going to write some tests as I extend behavior on “an existing product” and also write tests for some untested code. I’ll be using my favorite boilerplate code–the .NET Core CLI Angular template–as my existing product, as it provides a functional appliction with some existing tests for us to build on.

If you haven’t already, start by creating a new Angular application by running the following command:

dotnet new angular -o my-app

Verify that can run your new application by running dotnet run in the my-app directory. my-app/ClientApp contains the Angular application. Since we’re going to be adding to existing test suite, we should verify that the existing tests run and pass. Run the following from my-app/ClientApp:

npm install
ng test

You should see output like the following, indicating that all tests have passed.

Now that we’ve verified that existing tests work, we can start making changes. Let’s assume we want to modify the Counter page to have a decrement button in addition to its increment button, because sometimes we click too many times. Before we start making changes to the Counter component itself, we can describe the desired behavior in the existing counter.component.spec.ts file, which already contains similar logic for the increment functionality. Most of what needs to be written can be copied and adjusted from the Increment test.

Here’s the test I wrote:

it ('should decrease the current count by 1 when Decrement is clicked', async(() => {
  const countElement = fixture.nativeElement.querySelector('strong');
  expect(countElement.textContent).toEqual('0');

  const decrementButton = fixture.nativeElement.querySelector('#decrement-button');
  decrementButton.click();
  fixture.detectChanges();
  expect(countElement.textContent).toEqual('-1');
}));

I can run tests again, and guess what–it’ll fail. Cool. So let’s make it work, which is just two steps. First we need to add the button to counter.component.html:

<h1>Counter</h1>

<p>This is a simple example of an Angular component.</p>

<p aria-live="polite">Current count: <strong>{{ currentCount }}</strong></p>

<button class="btn btn-primary" (click)="incrementCounter()">Increment</button>

<button class="btn btn-secondary" (click)="decrementCounter()" id="decrement-button">Decrement</button>

And then we need to add the logic for when it’s clicked in counter.component.ts:

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

@Component({
  selector: 'app-counter-component',
  templateUrl: './counter.component.html'
})
export class CounterComponent {
  public currentCount = 0;

  public incrementCounter() {
    this.currentCount++;
  }

  public decrementCounter() {
    this.currentCount--;
  }
}

That’s it. Now we can run ng test again and see that we now have 3 passing tests.

Good stuff. Now, let’s turn our attention to some untested code. FetchDataComponent is functional but has no tests for its display of data retrieved from the API. We’ll need to mock the API call to return some data and then assert that results are displayed as expected.

Here’s my fetch-data.component.spec.ts file with a test that mocks the API call and asserts that data is populated in the table on the UI:

import { async, ComponentFixture, TestBed } from '@angular/core/testing';
import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';

import { FetchDataComponent } from './fetch-data.component';

describe('FetchDataComponent', () => {
    let component: FetchDataComponent;
    let fixture: ComponentFixture<FetchDataComponent>;
    let httpMock: HttpTestingController;

    beforeEach(async(() => {
        TestBed.configureTestingModule({
            imports: [HttpClientTestingModule],
            declarations: [FetchDataComponent],
            providers: [{ provide: 'BASE_URL', useValue: 'https://my.fake.url/' }]
        }).compileComponents();
    }));

    beforeEach(() => {
        fixture = TestBed.createComponent(FetchDataComponent);
        component = fixture.componentInstance;
        httpMock = TestBed.get(HttpTestingController);
    });

    it('should retrieve weather forecasts', async(() => {
        const dummyForecasts = [
            {
                date: "date1",
                temperatureC: 0,
                temperatureF: 32,
                summary: "summary1"
            },
            {
                date: "date2",
                temperatureC: 100,
                temperatureF: 212,
                summary: "summary2"
            }
        ];

        const req = httpMock.expectOne('https://my.fake.url/weatherforecast');
        req.flush(dummyForecasts);

        expect(component.forecasts).toBe(dummyForecasts);
        fixture.detectChanges();
        const rowCount = fixture.nativeElement.querySelectorAll('table tr').length;
        expect(rowCount).toBe(3); // header plus two data rows
    }));
});

There’s a lot to unpack with this test, and I’m going to attempt to give a visual, summary-level explanation in the screenshot below.

Once again, we run tests using ng test and see that we now have passing tests for FetchDataComponent!

Installing Angular CLI on Ubuntu 18.04.4 LTS

I was all geared up to explore unit testing in Angular this morning–something I’ve been putting off learning for quite some time–and quickly hit an problem. I started by installing Angular CLI using apt install ng-common, but trying to use the Angular CLI’s ng command was launching Emacs!

It took me a minute to figure this out, and here’s what it took. First, I uninstalled:

sudo apt remove ng-common

Next, I installed using npm:

sudo npm install -g @angular/cli

This was common how-to-fix-it advice, but this didn’t resolve the problem for me. At this point ng was no longer launching an editor, but instead it was an unrecognized command. Luckily, I found the solution here.

I noticed in the install output that the bin location was listed. I was able to verify where the ng binary was located and add an alias. After that, ng --version worked successfully.

Here’s the alias I added to ~/.bashrc:

alias ng='/usr/local/lib/node_modules/@angular/cli/bin/ng'

Run an ASP.NET Core App on Raspberry Pi With Docker

In my last article, I wrote about how to create a single-page Angular app using the .NET Core CLI, create a Docker image, and run it as a container in about 4 steps that take just minutes to execute. By modifying a single line in your Dockerfile, you can target the 32-bit ARM architecture needed to run the image as a container on a Raspberry Pi.

Here’s the one line that needs to change in the Dockerfile to make it runnable on ARM32 (old line is commented for reference):

# FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 AS base
FROM mcr.microsoft.com/dotnet/core/aspnet:3.1.2-buster-slim-arm32v7 AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build
WORKDIR /src
COPY ["my-app.csproj", "./"]
RUN dotnet restore "./my-app.csproj"
COPY . .
WORKDIR "/src/."
RUN dotnet build "my-app.csproj" -c Release -o /app/build
RUN apt-get update && \
    apt-get install -y wget && \
    apt-get install -y gnupg2 && \
    wget -qO- https://deb.nodesource.com/setup_10.x | bash - && \
    apt-get install -y build-essential nodejs

FROM build AS publish
RUN dotnet publish "my-app.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "my-app.dll"]

Note that the official list of available tags for different architectures can be found here. Consult this list to determine if newer images are available.

That’s it, though. Create your image, push it to Docker Hub, pull it on your Raspberry Pi, and run it just as you would locally. If you haven’t used Docker Hub before, you’ll need to login and create a repository. Check out the Docker Hub Quickstart for help. You may also need to run docker login on both machines to access your new repo.

# dev machine
docker build -t <dockerID>/repo .
docker push <dockerID>/repo

# raspberry pi
docker pull <dockerID>/repo
docker run -d -p 5000:80 <dockerID>/repo
The default dotnet new Angular app running locally on Raspberry Pi.

10 Minutes to Create & Run .NET Core Angular SPA in Docker

In this article, I’ll demonstrate how to create an ASP.NET Core Angular single-page application using the .NET Core CLI, create a Docker image, and run it as a container. The entire process is just 4 steps, each of which takes about a minute to perform–although creating the Docker image takes a couple minutes to complete. Note, also, that these same steps work from both Linux and Windows.

  1. Create Angular application
  2. Create Dockerfile
  3. Create Docker image
  4. Run container

Before you start, make sure you have the following prerequisites installed.

  • .NET Core SDK
  • Visual Studio Code with Docker extension
  • Docker

Installation can be verified by running these commands:

dotnet --version
code --version
code --install-extension ms-azuretools.vscode-docker
docker --version

Create the Application

We begin by creating our Angular application using the dotnet new command and specifying the angular template. The -o argument will cause the new project to be created in a sub-folder named my-app. This will create a .NET Core ASP.NET project with an Angular app in its ClientApp folder. After running the command, go into the new directory and launch Visual Studio Code.

dotnet new angular -o my-app
cd my-app
code .

Add Docker Files

With the Docker extension for VS Code installed, you can add Docker files easily via the command palette. Open the command palette using ctrl+shift+P or View > Command Palette menu options, and run the command Docker: Add Docker Files to Workspace. (Tip: type “docker” to filter commands.)

Selecting the command will ask you a series of questions:

  • Application Platform: ASP.NET Core
  • Operating System: Linux
  • What port(s) does your app listen on? 80, 443

If you’re running Docker on Windows, it’s important to make sure Docker is configured to run the right type of containers (Windows vs Linux). I answered “Linux” above, and I can confirm that my Docker for Windows is configured to run Linux containers by clicking the Docker icon in my system tray, as shown in the screenshot below. It shows “Switch to Windows containers” which means it’s currently using Linux containers. It’s fine to use Windows containers, too, but you’ll need to adjust installation instructions for NodeJS in the Dockerfile further down.

Once you’ve answered the Docker extention’s questions, a Dockerfile is generated. One modification is needed to also install NodeJS for our client app. The lines needed to do this are highlighted in the complete Dockerfile below.

FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build
WORKDIR /src
COPY ["my-app.csproj", "./"]
RUN dotnet restore "./my-app.csproj"
COPY . .
WORKDIR "/src/."
RUN dotnet build "my-app.csproj" -c Release -o /app/build
RUN apt-get update && \
    apt-get install -y wget && \
    apt-get install -y gnupg2 && \
    wget -qO- https://deb.nodesource.com/setup_10.x | bash - && \
    apt-get install -y build-essential nodejs
    
FROM build AS publish
RUN dotnet publish "my-app.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "my-app.dll"]

Build the Image

When you’re done editing your Dockerfile in VS Code, save changes and head back to the command line. Run the following command to build your image:

docker build -t my-app .

Verify that the image was created by running another command:

docker image ls my-app

Run a Container

Now we’ll use the docker run command to run a container using our image. We’ll specify two arguments: -d to run in detached mode and -p to map ports on the local machine to the container.

docker run -d -p 5000:80 my-app

Verify that the app is running by browsing to the localhost:5000:

Broadcast Changes to Angular Factory Properties

I was making a little website with Angular the other day, and I wanted to have a search box in my nav bar that could be used from any page. When the search control is used, the user is sent to a search page that displays results but also lets users run additional searches. Both search functions use the same angular factory to execute their searches. Unfortunately, I was finding that the nav bar search control wouldn’t update search results when used from the search page.

I was able to solve the problem by using $broadcast and $on. It’s pretty simple, and it looks a lot cleaner than a lot of $watch solutions that I ran into while looking for a solution.

Here’s what my factory looks like:

app.factory('searchService', ['$rootScope', '$http', function ($rootScope, $http) {
    var factory = {
        search: search,
        getResults: getResults
    };
    
    var _results = [];
    
    function search(criteria) {
        return $http.post(_serviceBase + 'api/search', criteria).then(function (results) {
            _results = results.data;
            $rootScope.$broadcast('searchCompleted', _results);
            return results;
        });
    };

    function getResults() {
        return _results;
    }

    return factory;
}]);

And here’s my searchController that handles the broadcast event with $on:

app.controller('searchController', ['$scope', 'searchService', function ($scope, searchService) {
    $scope.criteria = {};
    $scope.results = searchService.getResults();

    $scope.search = function () {
        searchService.search($scope.criteria).then(function (results) {
            $scope.results = results.data;
        }, function (error) {
            console.error(error.data.message);
        });
    };

    $scope.$on('searchCompleted', function (results) {
        $scope.results = searchService.getResults();
    });
}]);

Note the use of $rootScope in the factory. Broadcasting the change is a single line of code, and handling the event in relevant controllers is pretty simple, too. Nice!