Facade Pattern
The facade pattern (also spelled façade) is a software-design pattern commonly used in object-oriented programming. Analogous to a facade in architecture, a facade is an object that serves as a front-facing interface masking more complex underlying or structural code.
The facade pattern is typically used when:
- a simple interface is required to access a complex system,
- a system is very complex or difficult to understand,
- an entry point is needed to each level of layered software, or
- the abstractions and implementations of a subsystem are tightly coupled.
Example
class Grinder {
String _type;
Grinder(this._type);
void grind() {
print("Grinding $_type!");
}
}
class Maker {
String _type;
Maker(this._type);
void fill() {
print("Filling the $_type maker!");
}
void retrieve() {
print("Retrieving the $_type!");
}
void start() {
print("Starting the $_type maker!");
}
}
class Imbiber {
String _beverage;
Imbiber(this._beverage);
void drink() {
print("Mmmmm...drinking $_beverage!");
}
}
class MorningFacade {
final _coffeeDrinker = Imbiber("coffee");
final _coffeeGrinder = Grinder("coffee beans");
final _coffeeMaker = Maker("coffee");
void prepareCoffee() {
print("\r\nPreparing the coffee...");
_coffeeGrinder.grind();
_coffeeMaker
..fill()
..start();
print("Coffee is brewing!\r\n");
}
void drinkCoffee() {
print("\r\nMust...have...coffee...");
_coffeeMaker.retrieve();
_coffeeDrinker.drink();
print("This is damn fine coffee!");
}
}
void main() {
var typicalMorning = MorningFacade();
print("Wake up! Grab a brush and put on a little makeup...");
print("\r\nStumble to the kitchen...");
typicalMorning.prepareCoffee();
print("Oh my...that smells good...");
typicalMorning.drinkCoffee();
print("\r\nI'm ready to attack the day!");
}