data_monitor 2.2.2

A Data Monitor package that encapsulates Annotations, Example and Utilities.

Details

This package allows Flutter projects to utilize State Management to overcome some of the limitations enforced by the framework.

Its main use is to create data repositories or models that allow callers to be notified when changes are made to member fields. These changes are tracked internally and cause Widgets that use the data to be rebuilt.

No more calls to setState().

Features

Can be used (with more efficiency) to rebuild StatelessWidget. You can remove all the verbose State code that is usually associated with a StatefulWidget.

Getting started

The package is very simple to use. Just add code like the following to create your data model class:

class ModelData extends _ModelData with _$ModelData
{
  // Other methods etc for class
}

@dataMonitor
abstract class _ModelData extends DataNotifier
{
  @monitor
  int count = 0;

  @monitor
  String name = 'A Name';
}

Propagating Changes to Property Values

When a property value changes, you can ask for its new value to be propagated. This allows 'side-effects' or cascades to be implemented. A really simple example can be found in the /example directory.

Note: @propagate properties @monitor their value at the same time as providing their extra function. As such, they also respect @cache properties (see below).

@dataMonitor
abstract class _ModelData extends DataNotifier
{
  @propagate
  String firstName = 'Joe';

  void firstNamePropagate(String value)
  {
    // Do something useful with the new value,
    // like setting derived properties
  }
}

Caching Property Getters

You can cache property 'values' internally to great effect, when used correctly. For example, if you had to collect data from a source that is slow or complicated, you could use the following:

@dataMonitor
abstract class _ModelData extends DataNotifier
{
  @monitor
  String firstName = 'Joe';

  @monitor
  String lastName = 'Bloggs';

  @cache
  Future<String> get fullName async
  {
    // Performs a big task asynchronously, such as getting data
    // from an external database

    return await humungous(firstName, lastName);
  }
}

In this example, the return value from 'humungous' is cached and only ever recalculated when either 'firstName' or 'lastName' change.

Usage

A fully working Flutter Application that describes how to use the various features is available in the /example directory.

Additional information

You can also use the data_monitor_generators package to automatically generate boilerplate code from @annotations like the ones seen above (using build_runner).