享元模式从对象中剥离出不发生改变且多个实例需要的重复数据，独立出一个享元，使多个对象共享，从而节省内存以及减少对象数量。
flyweight.go
package flyweight import "fmt" type ImageFlyweightFactory struct { maps map[string]*ImageFlyweight } var imageFactory *ImageFlyweightFactory func GetImageFlyweightFactory() *ImageFlyweightFactory { if imageFactory == nil { imageFactory = &ImageFlyweightFactory{ maps: make(map[string]*ImageFlyweight), } } return imageFactory } func (f *ImageFlyweightFactory) Get(filename string) *ImageFlyweight { image := f.maps[filename] if image == nil { image = NewImageFlyweight(filename) f.maps[filename] = image } return image } type ImageFlyweight struct { data string } func NewImageFlyweight(filename string) *ImageFlyweight { // Load image file data := fmt.Sprintf("image data %s", filename) return &ImageFlyweight{ data: data, } } func (i *ImageFlyweight) Data() string { return i.data } type ImageViewer struct { *ImageFlyweight } func NewImageViewer(filename string) *ImageViewer { image := GetImageFlyweightFactory().Get(filename) return &ImageViewer{ ImageFlyweight: image, } } func (i *ImageViewer) Display() { fmt.Printf("Display: %s\n", i.Data()) }
flyweight_test.go
package flyweight import "testing" func ExampleFlyweight() { viewer := NewImageViewer("image1.png") viewer.Display() // Output: // Display: image data image1.png } func TestFlyweight(t *testing.T) { viewer1 := NewImageViewer("image1.png") viewer2 := NewImageViewer("image1.png") if viewer1.ImageFlyweight != viewer2.ImageFlyweight { t.Fail() } }
