Question

我有一个工厂方法，如下所示。有没有更好的方法来设计这个，所以我不必使用switch语句并实现开放封闭原则

public IPolicy CreatePolicy(Context context)
{
    IPolicy policy = default(IPolicy);
    ISettings settings = _settings.Get(context);
    Policy policyType = (Policy) Enum.Parse(typeof(Policy), settings.Policy);
    switch (policyType)
    {
        case Policy.Policy1:
            policy = new Policy1(_policy1Service, _logHandler);
            break;
        case Policy.Policy2:
            policy = new Policy2(_policy2Service, _logHandler);
            break;
        case Policy.Policy3:
            policy = new Policy3(_policy1Service, _policy2Service, _logHandler);
            break;
    }
    return policy;
}

Answer 1

假设枚举文字与您的类名完全相同，您可以根据枚举文字动态创建实例，如

public static IPolicy CreatePolicy(Policy policy)
{
    //Change this if the namespace of your classes differs
    string ns = typeof(Policy).Namespace;

    string typeName = ns + "." + policy.ToString();

    return (IPolicy)Activator.CreateInstance(Type.GetType(typeName));
}

只需像

那样添加构造函数参数即可

return (IPolicy)Activator.CreateInstance(Type.GetType(typeName),
    _policy1Service, _logHandler);

由于这是非常不寻常的，请考虑向IPolicy添加Initialize（...）方法以传递这些参数以允许空构造。

具有不同构造函数参数的类型的抽象工厂或工厂方法

1 个答案: