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Motion · 27 Remounting and State Restoration
Series contents · Technology map
Stage: Validating a Motion System · Editable example · Storage ID: motion-step-27
Goals and learning outcomes
- Learning outcome: Explain the role of Lifetime. Input case: Hiding and showing after reordering.
- Deliverable: A table of order, subscriptions, and focus restoration. Connect your rationale for handling Restoration to the code.
Prerequisites
Prepare the results of the Render cost and Measurement exercises from Unit 26, “Observing Renders and Performance”.
Key concepts and explanations
Lifetime
Removing a component ends the lifetime of its subscriptions and motion. Decide separately where data is stored.
Restoration
Decide whether the previous order should remain when the component reappears. Do not overuse key changes as an arbitrary reset mechanism.
Practice setup
First check the execution scope guidance on the example screen. The following describes the environment needed to extend the assignment in a separate project. The existing motion-01·02·03 examples are limited examples based on Motion JS animate. For React layout, AnimatePresence, and hooks exercises, install motion in a separate local React project and import from motion/react. Do not assume JSX runs directly in the editor; preserve CSP and isolation.
The linked example is a starting point. It does not implement every task below. Complete work beyond its supported scope in a separate project.
Practice tasks
- In src/day-27.tsx of a separate exercise project, connect a board visibility toggle to order state above the board and remount 5 times. Use the existing Unit 1·14·28 examples only as starting points.
- Input condition: Hiding and showing after reordering. Baseline: Inside the card. Run under the baseline condition, then record observations and errors in notes/day-27.md.
- Variable to change: State location; new value: Above the board. Run again with the same input path. Deliverable to save: A table of order, subscriptions, and focus restoration. Hypothesis to test: The order is preserved after the board reappears. Compare it with the actual results and record whether they agree and the causes of any differences.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| State location | Inside the card | Above the board | The order is preserved after the board reappears. |
Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.
Completion criteria
- Required deliverable: A table of order, subscriptions, and focus restoration. You have results for both the baseline and changed conditions, allowing a comparison of 2 conditions, and have recorded the input values and execution environment.
- Your explanation of the differences between the two conditions connects both concepts: Lifetime and Restoration. For unexpected items, give at least 1 cause or reason they remain unresolved.
Self-check
- Which processing stage does Lifetime affect in this exercise? Input case: Hiding and showing after reordering.
- Variable to change: State location. Hypothesis to test: The order is preserved after the board reappears. Did the actual results agree with the hypothesis? Explain your evidence in terms of Restoration.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
Interactive Remounting and State Restoration experiment with cleanup of the resources used.
Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.
Next learning
Previous: Observing Renders and Performance · Next: Gestures and Accessibility