gistfile1.java

// 2. Double Dispatch 방식 리팩토링 

NewPrescription prescription = new NewPrescription();
assertEquals("two pill a day", prescription.getPrescription(new SeriousPatientStatus(),  new AdultPatientType()));
assertEquals("one pill a day", prescription.getPrescription(new MildPatientStatus(), new AdultPatientType()));
assertEquals("one pill a day", prescription.getPrescription(new SeriousPatientStatus(), new ChildPatientType()));
assertEquals("half pill a day", prescription.getPrescription(new MildPatientStatus(), new ChildPatientType()));

public class NewPrescription {
  public String getPrescription(PatientStatus status, PatientType type) {
    return status.getPrescriptionWith(type);
  }

  public double getMaxIngestionPerDay(PatientStatus status, PatientType type) {
    return status.getMaxIngrestionPerDayWith(type);
  }
}

public class SeriousPatientStatus implements PatientStatus {
	@Override
	public String getPrescriptionWith(PatientType type) {
		return type.getPrescriptionSerious();
	}

	@Override
	public double getMaxIngrestionPerDayWith(PatientType type) {
		return type.getMaxIngrestionSerious();
	}
}

public class ChildPatientType implements PatientType {

	@Override
	public String getPrescriptionSerious() {
		return "one pill a day";
	}

	@Override
	public double getMaxIngrestionSerious() {
		return 1;
	}

	@Override
	public String getPrescriptionMild() {
		return "half pill a day";
	}

	@Override
	public double getMaxIngrestionMild() {
		return 0;
	}
}