![]() The Products file is too long, so we cut it short for brevity. import 'package:flutter/foundation.dart' The Product class is the parent class based on which we have added a list of Products. In our models folder we have two files Product and Products. Keeping other files intact, you can run the main dart file and get the same result.įirstly, we must have a data model at our local storage. We’ve created a folder branch-one where we keep the main dart file for this example. But instead of passing data through class constructor, we’ll rely on provider package with the help of ChangeNotifierProvider and ChangeNotifier.īefore we start, let me tell you where you’ll find the source code. We’re going to design a shop app where we we’ll have some products. Let’s have a look at how we can provide the current data model to anywhere in our widget tree. In this very short, but important article on Provider pattern flutter we’ll quickly learn the concept. It is true that provider package with the help of ChangeNotifierProvider and ChangeNotifier manages state most efficiently.īut provider is actually a flutter architecture that provides the current data model to the place where we need it. Its check is not mandatory but it’s better to rebuild a widget only when it’s really necessary, isn’t it? If the value is the same it’s not necessary to call notifyListeners().In Flutter when we discuss provider pattern to give examples of provider, we usually think of state management. ![]() When the new value is assigned to the value notifyListeners() is called after comparing the current value. I created the following class which can be used for a primitive data type. notifyListeners() needs to be called for that. We need to extend ChangeNotifier class in order to notify the value change. To avoid such a case, it should be placed one level above where the value is actually needed. However, if the provider is placed at the top of the tree all widgets can consume the value. Provider must be placed higher place than Consumer. Consumer can recreate their own widgets by using the updated value. Provider notifies the value change to the consumer when the target value changes. Those are the target widgets that we want to update. ![]() We can easily achieve that if we use Provider. If we use InheritedWidget we can solve this problem but it requires boilerplate code. However, it doesn’t work if the target data that the blue button wants to update is used by another widget. ![]() If we extract Box1 and blue Button into another class together we can rebuild only them. If possible, we want to rebuild only the necessary widget. If the blue button is clicked to update the value of Box1 which is highlighted with red color and setState is called on the event, all widgets listed here are rebuilt. All widgets are defined in the same class. It takes longer to complete to rebuild all widgets than to rebuild only one widget. If the parent widget is rebuilt all child widgets are rebuilt even if the rebuild is not necessary for some of them. It means that setState needs to be called in the widget or parent widget. Why is provider necessary in the first place? When one of the values on a view needs to change, its item needs to be rebuilt. ChangeNorifier that have more than 2 properties. ![]()
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