什么是颤振中的 BLOC 模式？

Question

I'm trying to understand the bloc pattern but unable to understand. Browsed many tutorial but couldn't understood properly. I just understood that

1. bloc pattern is used to managing the state of app. and

2. for take input, use sink and for output, we use Stream by stream controller.

and not sure I'm getting wrong or right.

But clear thing is that, it's not enough for acquaintance of bloc pattern.

Explain it with simple language.

Answer 1

The Business Logic Component (BLoC) pattern is a pattern created by Google for state management.The BLoC pattern uses Reactive Programming to handle the flow of data within an app.

1. A BLoC stands as a middleman between a source of data in your app (eg an API response) and widgets that need the data.
2. A BLoC has two simple components: Sinks and Streams. Input of BLoC is sink and output is stream.
3. User inputs are given to the BLoC by adding data to the sink --> business logic is in the bloc which processes data --> Widgets listening to the streams will be notified with the processed data.
4. In other words, it receives streams of events/data from the source, handles any required business logic and publishes streams of data changes to widgets that are interested in them.

Here is a wonderful article that has an example that you can refer to understand BLoC better.

BLoC can be implemented using StreamBuilder and StreamController but you should use flutter_bloc flutter package to cut the boilerplate code. examples .

I hope this helps, in case of any doubts please comment. If this answer helps you then please accept and up-vote it.

Answer 2

• Bloc makes it easy to separate presentation from business logic, making your code fast, easy to test, and reusable.
• Bloc attempts to make state changes predictable by regulating when a state change can occur and enforcing a single way to change state throughout an entire application.

You can read more here , it is easy to understand

Answer 3

it is a way to communicate between your logic and UI and change the UI base on your logic or vice versa in flutter, you will need to change your widget's (User interface) base on the some logic for example if user clicks on the A show the B text the or vice versa for example if year is 2020 show 2020 text to user bloc is just a pattern that helps you to accomplish this (whit some positive and some negative points) and there are lots of patterns other than bloc that will do this job for you

you could study about state and what is state management and why we need it? in the state management section of the flutter documents link here:

also bloc library official documents are a good place to start learning about the bloc. link here :

Answer 4

BLOC is another state management pattern used by many for flutter and angular.

In simple words it allows you to update specific widgets when some specific state is declared by the bloc. You can dispatch an event to change the state of the widget which is wrapped with BlocBuilder .

For doing some process other than building widgets, you can use BlockListener and do the process you want based on the state declared by the bloc.

You can learn more about it here: https://bloclibrary.dev/#/gettingstarted