Why Component Libraries Exist
A component library is a special canvas app whose sole purpose is to define and publish reusable components, so that visual and behavioral consistency doesn't depend on every maker rebuilding the same controls from scratch in every app. Once published and imported, a component behaves like a native control that any consuming app can drop onto a screen and configure.
Cricket analogy: A component library is like a franchise's standardized training academy — every player (app) that draws from it learns the exact same batting technique instead of each coach inventing their own drills.
Building Custom Components
Components are built on a dedicated component-editing canvas, where you place and group several standard controls — labels, images, buttons, galleries — into one named unit, such as PlayerCard. Once grouped, the component can be placed on any screen, and every placed instance shares the same underlying layout and logic defined once inside the component canvas.
Cricket analogy: Grouping a label, image, and button into one component named 'PlayerCard' is like packaging a bowler's entire pre-delivery routine into one repeatable action instead of separate uncoordinated steps.
// Custom property definitions on a component named "RatingStars"
// Input property: MaxRating (Number)
// Output property: SelectedValue (Number)
// Inside the component, a Gallery's Items property:
Sequence(RatingStars.MaxRating)
// Consuming app screen reads the output property:
Label1.Text = "You rated: " & RatingStars1.SelectedValueCustom Properties: Input, Output, and Behavior
Custom properties make a component configurable: Input properties (like MaxRating) pass configuration values in, Output properties (like SelectedValue) report data or state back out to the host app, and Behavior properties (like OnRatingChanged) let the component raise an event the host app can respond to. Together these three types turn a static grouping of controls into a fully parameterized, interactive building block.
Cricket analogy: An input property like MaxScore is like giving a net bowler a target line to bowl at — the component receives that configuration value and adjusts its behavior accordingly each time it's placed.
Input properties configure a component's appearance or behavior when it's placed; Output properties expose values the component computes back to the host; Behavior properties act like events, letting the host app run custom logic (e.g. calling a flow) in response to something happening inside the component.
Publishing, Importing, and Versioning
After editing a component in its library and clicking Publish, the new version doesn't automatically appear in apps that already imported it — each consuming app must explicitly reimport the library to pick up the update. This deliberate, manual model prevents an in-progress library edit from silently breaking every app that depends on it.
Cricket analogy: Publishing a new library version is like releasing an updated coaching manual — teams (apps) that already trained under the old edition keep using it until they deliberately reimport the new one.
Renaming or removing a custom property in a published library is a breaking change for every app that already imports that component; test changes in a non-production app first, and coordinate a reimport across all consuming apps before rolling a breaking update out broadly.
- A component library is a canvas app of type 'Component library' dedicated to defining reusable components.
- Custom properties are Input (configuration in), Output (data/state out), or Behavior (event triggers like OnReset).
- Apps must explicitly reimport an updated library — changes never propagate automatically to already-placed components.
- Removing or renaming a custom property is a breaking change for every app that already imports that component.
- Grouping controls into named components centralizes design and logic, keeping many apps visually and behaviorally consistent.
- Component libraries can be added to a solution for versioned, coordinated ALM deployment.
- Plan a communication process so app owners know when a breaking library update requires reimport.
Practice what you learned
1. What type of custom property lets a component report a value back to the app that uses it?
2. What happens to an app when the component library it imported from is updated and republished?
3. Which custom property type is used for firing an event like OnRatingChanged?
4. What is a component library, structurally, in Power Apps?
5. What is a key risk of removing a custom property from a published component library?
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