直截了當的告訴你什麼是工廠模式

千萬不要以為創建一個類，以Factory為後綴就是工廠，那不是工廠。

直接演示：

public interface IMachine
{
string Name { get; }
///

void TurnOn;
}

public class Computer : IMachine
{
public string Name
{
get { return "戴爾"; }
}

public void TurnOn
{
Console.WriteLine("電腦啟動");
}
}
public class Mobile : IMachine
{
public string Name
{
get { return "魅族"; }
}

public void TurnOn
{
Console.WriteLine("手機啟動");
}
}
public class UnknownMachine : IMachine
{
public string Name
{
get { return "機器故障" }
}

public void TurnOn
{
Console.WriteLine("啟動失敗");
}
}

class Program
{
static void Main(string[] args)
{
string description = "computer";
IMachine machine = GetMachine(description);
machine.TurnOn;

Console.ReadKey;
}
private static IMachine GetMachine(string description)
{
switch (description)
{
case "computer":
return new Computer;
case "mobile":
return new Mobile;
default:
return new UnknownMachine;
}
}
}

上面代碼一執行，IMachine介面里裝的Computer，所以電腦啟動了

工廠模式登場

public class MachineFactory
{
private Dictionary _machines;

public MachineFactory
{
LoadTypesICanReturn;
}

public IMachine CreateInstance(string description)
{
Type t = GetTypeToCreate(description);

if (t == null)
return new UnknownMachine;

return Activator.CreateInstance(t) as IMachine;
}

private Type GetTypeToCreate(string machineName)
{
foreach (var machine in _machines)
{
if (machine.Key.Contains(machineName))
{
return _machines[machine.Key];
}
}

return null;
}

private void LoadTypesICanReturn
{
_machines = new Dictionary;

Type typesInThisAssembly = Assembly.GetExecutingAssembly.GetTypes;

foreach (Type type in typesInThisAssembly)
{
if (type.GetInterface(nameof(IMachine)) != null)
{
_machines.Add(type.Name, type);
}
}
}
}

static void Main(string[] args)
{
string description = "Computer";
IMachine machine = new MachineFactory.CreateInstance(description);
machine.TurnOn;

Console.ReadKey;
}

CreateInstance方法也可以設計成靜態的

MachineFactory.CreateInstance(description);

在抽象一點可以讓MachineFactory實現IMachineFactory介面

public interface IMachineFactory
{
IMachine CreateInstance(string description);
}

public class MachineFactory : IMachineFactory

static void Main(string[] args)
{
string description = "Computer";
IMachine machine = LoadFactory.CreateInstance(description);
machine.TurnOn;

Console.ReadKey;
}

private static IMachineFactory LoadFactory
{
string factoryName = Properties.Settings.Default.DefaultMachineFactory;
return Assembly.GetExecutingAssembly.CreateInstance(factoryName) as IMachineFactory;
}

如果沒有上面的IMachineFactory介面，那麼具體的工廠將與其生產的具體類型緊密耦合，我認為這也是可以接受的。好了。就是這麼直截了當，簡單粗暴。

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