Documentation
¶
Overview ¶
Package memento implements the Memento design pattern. The Originator, WeatherMonitor, retrieves current weather forecasts from an external source (represented by RandomWeatherProvider, which implements the ForecastProvider interface) and can create a Snapshot (the Memento) of its current state by delegating to a Caretaker — the SnapshotHistory. The Caretaker is responsible for serializing and deserializing snapshots (mementos) from its internal storage and providing them back to the Originator when needed. The Snapshot remains opaque to the outside world due to base64-encoded state serialization.
Index ¶
Constants ¶
const ( Clear byte = iota Cloudy Rain ThunderStorm Snow SnowStorm )
Precipitation state enums.
Variables ¶
This section is empty.
Functions ¶
Types ¶
type Caretaker ¶
Caretaker defines a common interface for objects responsible for storing and restoring snapshots (mementos).
type Forecast ¶
type Forecast struct {
Temperature float32
Humidity float32
WindSpeed float32
Pressure int
Precipitation Precipitation
}
Forecast is the changeable state, that represents the specific weather forecast (and is the subject of memento).
type ForecastProvider ¶
type ForecastProvider interface {
Retrieve() *Forecast
}
ForecastProvider defines a common interface for components that can supply weather forecast data.
type Originator ¶
type Originator interface {
Update(*Forecast)
Print()
Snapshoter
ForecastProvider
}
Originator represents an entity whose state can be saved and restored using snapshots (mementos).
type Precipitation ¶
type Precipitation struct {
State byte
}
Precipitation is the stringifiable part of the Forecast.
func (*Precipitation) String ¶
func (p *Precipitation) String() string
String implements Stringer interface for the Precipitation.
type RandomWeatherProvider ¶
type RandomWeatherProvider struct{}
RandomWeatherProvider implements ForecastProvider interface and generates random forecast.
func (*RandomWeatherProvider) Retrieve ¶
func (r *RandomWeatherProvider) Retrieve() *Forecast
Retrieve creates the random weather Forecast.
type Snapshot ¶
type Snapshot struct {
Serialized string
}
Snapshot is a serialized memento capturing the state of a Forecast.
func NewSnapshot ¶
NewSnapshot is the Snapshot constructor.
type SnapshotHistory ¶
type SnapshotHistory struct {
// contains filtered or unexported fields
}
SnapshotHistory is the concrete Caretaker that manages Snapshot mementos — aggregating, serializing, and restoring them as needed.
func (*SnapshotHistory) Load ¶
func (s *SnapshotHistory) Load(index int) *Forecast
Load deserializes and returns the state from the specific Snapshot memento by index from the internal storage.
func (*SnapshotHistory) Save ¶
func (s *SnapshotHistory) Save(forecast *Forecast)
Save serializes and stores the specific Forecast state into the Snapshot memento inside the internal storage.
func (*SnapshotHistory) String ¶
func (s *SnapshotHistory) String() string
String implements Stringer interface for SnapshotHistory.
type Snapshoter ¶
type Snapshoter interface {
TakeSnapshot()
RestoreSnapshot(index int)
}
Snapshoter defines the ability to create and restore snapshots of internal state.
type WeatherMonitor ¶
type WeatherMonitor struct {
// contains filtered or unexported fields
}
WeatherMonitor is the specific Originator, responsable for the retrieval of the current weather Forecast from the external forecast providers. It is also allowed to Print the current Forecast, save Forecast snapshot through the Caretaker and restore the Forecast state from the snapshot.
func NewWeatherMonitor ¶
func NewWeatherMonitor(provider ForecastProvider) *WeatherMonitor
NewWeatherMonitor constructs the new WeatherMonitor structure.
func (*WeatherMonitor) Print ¶
func (w *WeatherMonitor) Print()
Print allows to print the current forecast state and the Caretaker state to screen.
func (*WeatherMonitor) RestoreSnapshot ¶
func (w *WeatherMonitor) RestoreSnapshot(index int)
RestoreSnapshot updates the current Forecast from the Snapshot, retrieved from the Caretaker.
func (*WeatherMonitor) Retrieve ¶
func (w *WeatherMonitor) Retrieve() *Forecast
Retrieve is fetching the current weather forecast from the external ForecastProvider and stores it as the current Forecast state.
func (*WeatherMonitor) TakeSnapshot ¶
func (w *WeatherMonitor) TakeSnapshot()
TakeSnapshot saves current Forecast as the new Snapshot memento, with help of the Caretaker.
func (*WeatherMonitor) Update ¶
func (w *WeatherMonitor) Update(forecast *Forecast)
Update mutates the current forecast in the Weather Monitor.
Source Files