Gotchas

invalidate([]) is a no-op

An empty prefix matches nothing. Use cache.clear() to wipe everything.

No effect

// This does nothing: an empty prefix matches no key
cache.invalidate([])

Correct

// Use clear() to wipe the entire cache
cache.clear()

invalidate() is prefix-based, not exact-match

A prefix matches every key that starts with it, including nested sub-keys.

// invalidate(['order', 'details', '42']) also matches:
//   ['order', 'details', '42']
//   ['order', 'details', '42', 'comments']
//   ['order', 'details', '42', 'attachments']
//
// It does NOT match:
//   ['order', 'details', '43']
//   ['order', 'list']

ref.set() and ref.update() write to the cache

They update both the Angular resource and the DataCache. Optimistic values survive cache version bumps from unrelated invalidations. Call invalidate() to trigger a fresh server fetch.

// set() and update() write to both the Angular resource AND the DataCache.
// Optimistic values survive cache version bumps from unrelated invalidations.
ref.set(newValue)
ref.update(prev => ({ ...prev, name: 'updated' }))

// To trigger a fresh server fetch after an optimistic update:
cache.invalidate(['order', 'details', '42'])

Cache keys are untyped at the boundary

DataCache stores unknown internally. Type correctness depends on consistent key-to-type pairings in your code.

// Nothing prevents this: both compile fine
cache.set(['user', '1'], { name: 'Alice' })       // User
const entry = cache.get<Order[]>(['user', '1'])  // reads as Order[]

// Convention: one key prefix per type, enforced in your API service