Component Best Practices

Good components need to be designed well. Taking the time to think of future use cases significantly enhances the components usability.

For Third-Party Library Integration: See the complete guide: Creating Components with Third-Party Libraries with full FullCalendar, Chart.js, and Leaflet examples.

Sizing and Styling

Generally, it should be the implementation of the component that is responsible for the component's size. There are some exceptions. This means that the width of your component is generally full width and the parent or 'implementor' of the component will control the width.

Examples:

Component Type	What sets size	Comments
Page Header Component	Parent	this allows the header
Button Component	Component	Buttons generally don't take on the shapre of the parent elements. When you need to override a buttons width, you can pass in a class.
Toggle switch	Component	Generally this type of component woudl not adapt its size to the parent
Toggle switch Array	Parent	An array of toggles would wrap or flow based on the containing element

Actions

Lifecycle & Async

• Use onBeforeMount for blocking setup (library load, data fetch); it awaits before render. Use onMount for DOM work after render.

• Always await async work inside function actions to preserve order; bfcomponent lifecycle dispatch already awaits ACTIONS_QUEUE.

• Load external libraries with BF.libraryLoadOnce(); no extra singleton guard needed for identical URLs.

Schema in Actions

• Lifecycle actions receive the component schema on action.schema (and action.options._componentSchema).

• Template-triggered actions: pass schema explicitly when needed, e.g. @click="namedAction('doThing', { schema, foo: 'bar' })".

• In functions, read with: const schema = action.schema || action.options._componentSchema || action.options.schema || {};.

DOM & Refs

• this.$refs is not available in namedAction functions. Use DOM queries: document.getElementById(...) or querySelector(...).

• Give stable IDs in your HTML if you need to target elements from actions.

EventBus & async namedActions

• runUtilityHook (and similar) support callbacks; wrap in a Promise:

  const result = await new Promise((resolve, reject) => {
    EventBus.$emit('runUtilityHook', payload, (res) => res?.error ? reject(res.error) : resolve(res));
  });

  This keeps async actions serialized with lifecycle dispatch.

Context

• Avoid this inside namedAction functions; rely on injected vars: model, app, document, window, BF, _, and schema (lifecycle only).

• Keep global/window writes idempotent; guard with window.__bfSingletons only for truly global resources (e.g., registering Vue components).

• For third-party instances (charts, uploaders), prefer per-instance scoping instead of global singletons.

Multi-Instance Components

• If the same component renders multiple times, add a unique instanceId (or similar) in schema and namespace any globals/hosts/plugins with it.

• Example pattern: const key = 'uppy_' + instanceId; window[key] = new Uppy.Uppy(...); hostId = 'bf-fileinput-host-' + instanceId;.

File Upload (Uppy + S3/FM)

• Fetch presigned URLs via runUtilityHook; await via the EventBus callback pattern above.

• Prefer dual URLs from backend: url (PUT, short expiry) and downloadUrl (GET, longer expiry) so users can view after upload.

• Namespace Uppy instances per instanceId; create per-instance hidden hosts to avoid conflicts when multiple upload buttons exist.