Foundations of Programming - Karl Seguin

Chapter 4 - Dependency Injection
worry, you won’t actually have to create mock implementations of each component, but for now it
keeps things obvious):
internal interface IDataAccess
{
int Save(Car car);
void Update(Car car);
}
internal class MockDataAccess : IDataAccess
{
private readonly List _cars = new List();
}
public int Save(Car car)
{
_cars.Add(car);
return _cars.Count;
}
public void Update(Car car)
{
_cars[_cars.IndexOf(car)] = car;
}
Although our mock’s upgrade function could probably be improved, it’ll do for now. Armed with this
fake class, only a minor change to the Car class is required:
public class Car
{
private int _id;
private IDataAccess _dataProvider;
public Car() : this(new SqlServerDataAccess())
{
}
internal Car(IDataAccess dataProvider)
{
_dataProvider = dataProvider;
}
public void Save()
{
if (!IsValid())
{
//todo: come up with a better exception
throw new InvalidOperationException("The car must be in a valid
state");
}
if (_id == 0)
{
Foundations of Programming Copyright © Karl Seguin www.codebetter.com
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