With the current builders object factories are always asked a new object, the problem is that the programmer does not always want a new object, that gives us the advantage to pick up theobjects housed in the cache: There are several design patterns to do this correctly, but Dartmakes it easy with special constructs for factories. (Colloquially called constructors without tears).
The instance creation expressions are based on interfaces and minimizes the need fordependency injection.
Example of use of factory:
interface Person factory PersonFactory{
Person(name);
final name;
}
class PersonFactory{
factory Person(name){
if(name== null) return const Ghost();
return new RealPerson(name);
}
}
class RealPerson implements Person{
RealPerson(this.name);
final name;
}
class Ghost implements Person{
const Ghost();
get name() => "ghost";
}
main(){
print(new Person("Pepita") is RealPerson);
print(new Person(null) is Ghost);
}
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