Skip to main content

A month of Flutter: post model and mock data

Originally published on
Now that there is a basic user interface, I'm going to create some mock data to display in it. The mock data will be stored in a JSON file and will include just the basic fields needed right now: idcreatedAtusernameimageUrl, and text. For imageUrl I grabbed some random images from Unsplashtext is actually empty as I haven't decided what text to use in the mocks yet.
This is a similar format to what you might expect from a JSON API. In the future there will probably be a User object and maybe an Image object that includes URLs to different sizes, etc.
    "id": "7d3d8bd1-b9a6-4e1f-8e4e-dca6f4861441",
    "imageUrl": "",
    "createdAt": "2018-12-09T15:35:54.006Z",
    "text": "",
    "username": "woodstock"
There are a number of ways to consume JSON in Flutter, but for now I'm going with the simple dart:convert pattern with a Post class.
class Post {
  const Post({
    @required this.username,
    @required this.createdAt,
    @required this.text,
    @required this.imageUrl,

  Post.fromMap(Map<String, dynamic> data)
      : id = data['id'],
        username = data['username'],
        createdAt = DateTime.parse(data['createdAt']),
        text = data['text'],
        imageUrl = data['imageUrl'];

  final String id;
  final String username;
  final DateTime createdAt;
  final String text;
  final String imageUrl;
I'm not a fan of optional values so I require everything. This way I don't have to check if a property exists; I just have to check that the property has a value I can work with.
Along with the default constructor I'm also defining a named constructorfromMap, that uses an an initializer listfromMap takes in a Map of the raw data and translates it to class variables. Note that the JSON datetime string is being converted to a Dart DateTime instance.
One downside of this code is there isn't a defined format for what the raw JSON data contains. For example, if I remove DateTime.parse the linter will not complain and there will be a failure at runtime when the createdAt string from the data tries to be set to the DateTime type property in Post. I have not yet found a way to define the key names and value types in a Map.
As the data model will change during development, it's important to make sure Post continues to work correctly. I will start with a pretty simple test. It loads the first mock data object, instantiates a Post instance, and asserts each value is available as expected. This is a plain Dart test (as opposed to a Flutter widget test) so I will have to add the Dart test package to dev_dependencies.
group('Post', () {
  test('fromMap', () async {
    final Post post = Post.fromMap(await postData());

    expect(, '7d3d8bd1-b9a6-4e1f-8e4e-dca6f4861441');
    expect(post.username, 'woodstock');
    expect(post.imageUrl, '');
    expect(post.createdAt, DateTime.parse('2018-12-09T15:35:54.006Z'));
    expect(post.text, '');
There is a new helper function, postData, that loads the JSON file, parses it, and returns the first object.
dynamic postData() async {
  final dynamic data = await File('../assets/posts.json').readAsString();
  return json.decode(data).first;
I've implemented the mock data in a JSON file instead of creating a List in Dart because that forces me to use the mock data in an asynchronous way. The real data will be async when pulled from Firestore so I am starting with that pattern now.

Code changes


Popular posts from this blog

Sync is currently experiencing problems

Update : I now recommend you install Google Chrome  and  disable  the built in Browser as it supports encrypting all synced data. After picking up a gorgeous  Galaxy Nexus yesterday I was running into an issue where my browser data wasn't syncing to the phone. After a little Googling I found this is commonly caused by having all of my synced Chrome data encrypted instead of the default of only encrypting the passwords. These are the steps I went through to get my dat syncing again without losing any of it. The exact error I was getting was "Sync is currently experiencing problems. It will be back shortly." In Google Chrome open the personal stuff settings page by clicking this link or by opening the wrench menu, and click on "signed in with".  Hit "disconnect your Google Account" to temporarily disable syncing from your browser. Visit the Google Dashboard and "Stop sync and delete data from Google". I waite

Installing Storytlr the lifestreaming platform

" Storytlr  is an open source lifestreaming and micro blogging platform. You can use it for a single user or it can act as a host for many people all from the same installation." I've been looking for something like Storytlr for a few months now or at least trying to do it with Drupal . While I love Drupal and FeedAPI  I did not want to spend all that time building a lifestream website. So I've been playing around with Storytlr instead and found it very easy. Here is how I got it up and running on a Ubuntu EC2 server. You can also check out the official Storytlr install instructions . Assumptions: LAMP stack installed and running. Domain setup for a directory. MySQL database and user ready to go. Lets get started! Get the code : wget tar -xvzf storytlr-0.9.2.tgz You can find out the  latest stable release  on Storytlr's downloads page. Import the database : Within protected/install is database.sq

A month of Flutter: a look back

Originally published on . This is it. 31 blog posts in 31 days. Writing  a month of flutter  has been a ton of work but also lots of fun and a good learning experience. I really appreciate how supportive and and positive everyone as been. Publishing experience For the series I've been posting on ,  DEV ,  my personal blog , and  Medium . After publishing to these sites, I would put the Bendyworks link on  Twitter ,  Reddit , and the  Flutter Study Group Slack . Posting to DEV was easy as they use Markdown just like the Bendworks blog. DEV also has built in support for a  series of posts  so it's easy to read the entire series. I did have to manually upload any embedded images. DEV also has a number of  liquid tags  for embedding things like GitHub issues that I didn't make as much use of as I should have. Blogger is rich text so it was easy to copy/paste the rendered posts. This would hotlink all the images though so I had to rem