Selective Rebuilds

Selective Rebuilds

Selective Rebuilds are a powerful optimization in Flutter Rocket that allows you to specify exactly which UI components should update when a model property changes. This prevents unnecessary rebuilds and keeps your app silky smooth, even with large data sets.

The Problem

In traditional state management, updating a single property in an object often triggers a rebuild of every widget listening to that object. If you have a list of 100 items and update the title of one item, you don't want to rebuild the entire list or even the entire list item widget if only a small part of it changed.

The Solution

Flutter Rocket solves this by allowing you to:

1. Register listeners for specific field names.
2. Notify listeners only for specific field names.

How to Implement

1. In your Model

Update your model's updateFields method to track changed fields.

void updateFields({String? titleField, String? bodyField}) {
  List<String> changedFields = [];
  
  if (titleField != null) {
    title = titleField;
    changedFields.add(postTitleField);
  }
  
  if (bodyField != null) {
    body = bodyField;
    changedFields.add(postBodyField);
  }
  
  // Notify only the widgets listening to these fields
  rebuildWidget(fields: changedFields.isEmpty ? null : changedFields);
}

2. In your UI

Wrap your specific UI components in RocketView and provide the fields list.

// This widget ONLY rebuilds when 'title' changes
RocketView(
  model: post,
  fields: [postTitleField],
  builder: (context, state) => Text(post.title!),
)

// This widget ONLY rebuilds when 'body' changes
RocketView(
  model: post,
  fields: [postBodyField],
  builder: (context, state) => Text(post.body!),
)

Why it's "Premium" Performance

• Reduced Build Time: Only the smallest necessary part of the UI tree is rebuilt.
• CPU Savings: Less work for the Flutter framework to diff the widget tree.
• Battery Efficiency: Lower energy consumption by minimizing rendering work.

Relationship with Automatic Bubbling

Selective Rebuilds used in conjunction with Automatic Bubbling provide the ultimate performance strategy:

• Bubbling ensures the parent (like a list) knows an item changed.
• Selective Rebuilds ensure that only the specific property inside that item is redrawn, rather than the entire list entry.

Pro Tip

Using Rocket CLI version 1.1.0 or higher will automatically generate the updateFields logic for you, making this optimization effortless.