func NewAlbum(folder string, dropbox *dropbox.Dropbox) *Album {
a := &Album{folder: folder, dropbox: dropbox, cache: rcache.New(folder)}
a.cache.RegisterFetcher(a.fetchOriginal)
a.cache.RegisterFetcher(a.fetchThumbnail)
expvar.Publish(fmt.Sprintf("photos (%s)", folder), expvar.Func(func() interface{} {
return a.photoMap
}))
return a
}
// The following example (pretends to) request images for a car, then has a
// dependent cache for thumbnails. If the original image is invalidated, so are
// the thumbnails.
func ExampleCache() {
c := rcache.New("mycache")
c.RegisterFetcher(func(key CarKey) ([]byte, error) {
return getCarImage(key.Manufacturer, key.Model), nil
})
c.RegisterFetcher(func(key ThumbnailKey) ([]byte, error) {
fullImage, _ := c.Get(CarKey{key.Manufacturer, key.Model})
return resize(fullImage, key.Size), nil
})
// Original image is only fetched once.
tx, _ := c.Get(CarKey{"BMW", "M5"})
t200, _ := c.Get(ThumbnailKey{"BMW", "M5", 200})
t400, _ := c.Get(ThumbnailKey{"BMW", "M5", 400})
fmt.Printf("%s + %s + %s", tx, t200, t400)
// Output: image:BMW.M5 + image:BMW.M5@200 + image:BMW.M5@400
}