News Glance

News Glance is a flutter app that lets you access the latest news and insights even from your home screen widget. It uses AI to generate a conclusion from the news headlines and allows you to view and share the articles.

PROJECT SPECIFICATION

• Programming language: Dart;

• SDK: Flutter;

• Interface: Flutter;

• Version control system: Git;

• Git Hosting Service: GitHub;

• RESTful API: News API;

• CI/CD: GitHub Actions is used to deliver new Android Package (APK) to Firebase App Distribution after every push to any other than the master branch, Codemagic is used to deliver new release app bundle to Google Play after every merge (push) to master branch;

• State management approach: BLoC;

• App testing platforms: Firebase App Distribution;

Code Readability: code is easily readable with no unnecessary blank lines, no unused variables or methods, and no commented-out code, all variables, methods, and resource IDs are descriptively named such that another developer reading the code can easily understand their function.

Getting Started

News Glance is an open source project and welcomes contributions from anyone who is interested. If you want to contribute to News Glance, you can follow these steps:

• Fork this repository and clone it to your local machine.
• Create a new branch for your feature or bug-fix.
• Make your changes and commit them with a clear and descriptive message.
• Push your branch to your forked repository and create a pull request to the master brunch.
• Wait for your pull request to be reviewed and merged.

Please follow the Flutter style guide when contributing to News Glance. You can also use the issues and discussions tabs to report bugs, request features, or give feedback.

Installation

To install News Glance, you need to have Flutter SDK and Android Studio installed on your machine. You can follow the official documentation to set up your development environment. To run a News Glance on your device or emulator, you need to clone this repository and open it in Android Studio. Then, you can use the run button or the command line to launch the app. For more information, see the Flutter documentation.

To create generated files, run:

dart run build_runner clean
dart run build_runner build --delete-conflicting-outputs

Test Coverage

Run tests, generate a code coverage report, and view that report in a web browser. This can be useful for checking which parts of the code are covered by tests and which parts might need more testing. Please note that you need to have lcov and genhtml installed on your system to use these commands. If they are not installed, you can usually install them with a package manager like apt or brew.

flutter test --coverage
genhtml coverage/lcov.info -o coverage
open coverage/index.html

Architectural pattern:

Onion Architecture

Layers

APPLICATION CORE - models, domain_services and application_services (core)

The number of layers in the application core will vary, but remember that the Domain Model is the very center, and since all couplings are toward the center, the Domain Model is only coupled to itself.

DOMAIN MODEL - models

In the very center, we see the Domain Model, which represents the state and behavior combination that models truth for the organization. Around the Domain Model are other layers with more behavior.

DOMAIN SERVICES - domain_services

The first layer around the Domain Model is typically where we would find interfaces that provide object saving and retrieving behaviour, called repository interfaces. The implementation of the object-saving behavior is not in the application core, however, because it typically involves a database. Only the interface is in the application core.

APPLICATION SERVICES - application_services

application_services is the layer outside domain_services. Application Services crosses the boundaries of the layers to communicate with Domain Services, however, the Dependency Rule is never violated. Using polymorphism, Application Services communicates with Domain Services using inherited classes: classes that implement or extend the repository presented in the Domain Services layer. Since polymorphism is used, the repository passed to Application Services still adhere to the Dependency Rule since as far as Application Services is concerned, they are abstract. The implementation is hidden behind the polymorphism.

UI, INFRASTRUCTURE, TESTS – lib, android, ios etc.

The outer layer is reserved for things that change often. These things should be intentionally isolated from the application core. We would find a class implementing a data source interface on the edge. This class implements the data source interface and is thereby coupled to it.

Style guides:

Style guide for Flutter, Dart style guide.

• DO use trailing commas for all function calls and declarations unless the function call or definition, from the start of the function name up to the closing parenthesis, fits in a single line.

• DON'T cast a nullable value to a non-nullable type. This hides a null check and most of the time it is not what is expected.

• PREFER using const for instantiating constant constructors

If a constructor can be invoked as const to produce a canonicalized instance, it's preferable to do so.

• DO sort constructor declarations before other members

• Avoid Mental Mapping

A single-letter name is a poor choice; it’s just a placeholder that the reader must mentally map to the actual concept. There can be no worse reason for using the name c than because a and b were already taken.

• Method names

Methods should have verb or verb phrase names like postPayment, deletePage, or save. Accessors, mutators, and predicates should be named for their value and prefixed with get…, set…, and is….

• Use Intention-Revealing Names

If a name requires a comment, then the name does not reveal its intent.

• Use Pronounceable Names

If you can’t pronounce it, you can’t discuss it without sounding like an idiot.

• Class Names

Classes and objects should have noun or noun phrase names and not include indistinct noise words:

GOOD:
Customer, WikiPage, Account, AddressParser.

BAD:
Manager, Processor, Data, Info.

• Functions should be small

Functions should hardly ever be 20 lines long. Blocks within if statements, else statements, while statements, and so on should be one line long. Probably that line should be a function call.

• Functions should do one thing

To know that a function is doing more than “one thing” is if you can extract another function from it with a name that is not merely a restatement of its implementation.

• One Level of Abstraction per Function

We want the code to read like a top-down narrative. We want every function to be followed by those at the next level of abstraction so that we can read the program, descending one level of abstraction at a time as we read down the list of functions.

• Dependent Functions

If one function calls another, they should be vertically close, and the caller should be above the callee, if possible.

• Use Descriptive Names

Don’t be afraid to make a name long. A long descriptive name is better than a short enigmatic name. A long descriptive name is better than a long descriptive comment.

• Function Arguments

The ideal number of arguments for a function is zero (niladic). Next comes one (monadic), followed closely by two (dyadic). Three arguments (triadic) should be avoided where possible.

GOOD:
includeSetupPage()

BAD:
includeSetupPageInto(newPageContent)

• Flag Arguments

Flag arguments are ugly. Passing a boolean into a function is a truly terrible practice. It immediately complicates the signature of the method, loudly proclaiming that this function does more than one thing. It does one thing if the flag is true and another if the flag is false!

GOOD:
renderForSuite()
renderForSingleTest()

BAD:
render(bool isSuite)

• Explain Yourself in Code

Only the code can truly tell you what it does. Comments are, at best, a necessary evil. Rather than spend your time writing the comments that explain the mess you’ve made, spend it cleaning that mess. Inaccurate comments are far worse than no comments at all.

BAD:
// Check to see if the employee is eligible
// for full benefits
if ((employee.flags & hourlyFlag) && (employee.age > 65))

GOOD:
if (employee.isEligibleForFullBenefits())

• TODO Comments

Nowadays, good IDEs provide special gestures and features to locate all the //TODO comments, so it’s not likely that they will get lost.

• Public APIs

There is nothing quite so helpful and satisfying as a well-described public API. It would be challenging, at best, to write programs without them.

/// dart doc comment

• Commented-Out Code

We’ve had good source code control systems for a very long time now. Those systems will remember the code for us. We don’t have to comment it out anymore.

• Position Markers

In general, they are the clutter that should be eliminated—especially the noisy train of slashes at the end. If you overuse banners, they’ll fall into the background noise and be ignored.

// Actions //////////////////////////////////

• Don’t Return Null

When we return null, we are essentially creating work for ourselves and foisting problems upon our callers. All it takes is one missing null check to send an app spinning out of control.

• Don’t Pass Null

In most programming languages, there is no GOOD way to deal with a null that is passed by a caller accidentally. Because this is the case, the rational approach is to forbid passing null by default. When you do, you can code with the knowledge that a null in an argument list is an indication of a problem, and end up with far fewer careless mistakes.

• Classes Should Be Small!

With functions, we measured size by counting physical lines. With classes, we use a different measure. We count responsibilities. The Single Responsibility Principle (SRP) states that a class or module should have one, and only one, reason to change. The name of a class should describe what responsibilities it fulfills. The more ambiguous the class name, the more likely it has too many responsibilities. The problem is that too many of us think that we are done once the program works. We move on to the next problem rather than going back and breaking the overstuffed classes into decoupled units with single responsibilities.

• Artificial Coupling

In general, an artificial coupling is a coupling between two modules that serves no direct purpose. It is a result of putting a variable, constant, or function in a temporarily convenient, though inappropriate, location. For example, general enums should not be contained within more specific classes because this forces the app to know about these more specific classes. The same goes for general purpose static functions being declared in specific classes.

• Prefer Polymorphism to If/Else or Switch/Case

There may be no more than one switch statement for a given type of selection. The cases in that switch statement must create polymorphic objects that take the place of other such switch statements in the rest of the system.

• Replace Magic Numbers with Named Constants

In general, it is a bad idea to have raw numbers in your code. You should hide them behind well-named constants. The term “Magic Number” does not apply only to numbers. It applies to any token that has a value that is not self-describing.

• Encapsulate Conditionals

Boolean logic is hard enough to understand without having to see it in the context of an if or while statement. Extract functions that explain the intent of the conditional.

GOOD:
if (shouldBeDeleted(timer))

BAD:
if (timer.hasExpired() && !timer.isRecurrent())

• Avoid Negative Conditionals

Negatives are just a bit harder to understand than positives. So, when possible, conditionals should be expressed as positives.

GOOD:
if (buffer.shouldCompact())

BAD:
if (!buffer.shouldNotCompact())

• Encapsulate Boundary Conditions

Boundary conditions are hard to keep track of. Put the processing for them in one place.

BAD:
if (level + 1 < tags.length) {
  parts = Parse(body, tags, level + 1, offset + endTag);
  body = null;
}

GOOD:
int nextLevel = level + 1;
if (nextLevel < tags.length) {
  parts = Parse(body, tags, nextLevel, offset + endTag);
  body = null;
}

• Constants versus Enums

Don’t keep using the old trick of public static final ints. enums can have methods and fields. This makes them very powerful tools that allow much more expression and flexibility.

Screenshots:

Screen Recording:

Download

Credits

This project is based on the codelab Adding a Home Screen widget to your Flutter App by Leigha Jarett and Eric Windmill.