c# - 在通用方法中返回接口(interface)继承的类

Question

我有 3 个非常相似的对象，只有一些差异

public class Person
{
    public Person(ResourceObject resource)
    {
        // resource comes from an API provided by one
        // of our systems (i have no control over it)
        this.ResourceObject = resource;
    }

    // Resource
    internal ResourceObject ResourceObject { get; }

    // Similar properties
    public string ObjectID { get; }
    public string ObjectType { get; }
    public IEnumerable<string> PropertyNames { get; }

    // Person-specific property example - Organisation
    public string Organisation { get; set; }
}

public class Computer
{
    public Computer(ResourceObject resource)
    {
        // resource comes from an API provided by one
        // of our systems (i have no control over it)
        this.ResourceObject = resource;
    }

    // Resource
    internal ResourceObject ResourceObject { get; }

    // Similar properties
    public string ObjectID { get; }
    public string ObjectType { get; }
    public IEnumerable<string> PropertyNames { get; }

    // Computer-specific property example - OperatingSystem
    public string OperatingSystem { get; set; }
}

public class Group
{
    public Group(ResourceObject resource)
    {
        // resource comes from an API provided by one
        // of our systems (i have no control over it)
        this.ResourceObject = resource;
    }

    // Resource
    internal ResourceObject ResourceObject { get; }

    // Similar properties
    public string ObjectID { get; }
    public string ObjectType { get; }
    public IEnumerable<string> PropertyNames { get; }

    // Group-specific property example - Members
    public string Members { get; set; }
}

我目前有GetPerson , GetComputer和 GetGroup有效的方法，但它们本质上做同样的事情，然后调用特定对象构造函数之一。为了深入研究泛型和接口(interface)的世界并了解更多(就像你一样)，我尝试创建一个 GetResource<T>方法可以完成与这 3 种方法相同的工作，而无需所有重复代码。

我创建了 IResource识别公共(public)属性的接口(interface):

public interface IResource
{
    string ObjectID { get; }
    string ObjectType { get; }
    IEnumerable<string> PropertyNames { get; }
}

然后尝试创建一个 GetResource<T>方法，但卡在了返回码处:

    public static T GetResource<T>(string identity) where T : IResource
    {
        // get resource from system API

        // and then return T somehow?
        return new T(resourceObject);
    }

我想改变 T 的返回值至 IResource但我仍然不确定我将如何确定返回哪个类(也许我需要一个基类？Resource 也许)。

我针对这种特定情况转向泛型的原因是，如果系统 API 更新并突然有一个新的 Location我不想创建 GetLocation 的对象方法，然后有 4 个方法，除了一行代码外，它们做的事情完全相同。

这是泛型的正确用例吗？如果是这样，我的方法如何确定要返回的对象？

Answer 1

使用基类来保存常见行为。

public abstract class Resource {

    protected Resource (ResourceObject resource) {
        // resource comes from an API provided by one
        // of our systems (i have no control over it)
        this.ResourceObject = resource;
    }

    // Resource
    internal ResourceObject ResourceObject { get; }

    // Similar properties
    public string ObjectID { get; }
    public string ObjectType { get; }
    public IEnumerable<string> PropertyNames { get; }
}

派生类

public class Person : Resource {

    public Person(ResourceObject resource):base(resource){
    }

    // Person-specific property example - Organisation
    public string Organisation { get; set; }
}

public class Computer : Resource {
    public Computer(ResourceObject resource) : base(resource) {
    }

    // Computer-specific property example - OperatingSystem
    public string OperatingSystem { get; set; }
}

public class Group : Resource {

    public Group(ResourceObject resource) : base(resource) {
    }

    // Group-specific property example - Members
    public string Members { get; set; }
}

接口(interface)无法初始化，因此尝试传递构造函数参数是行不通的。

有了基类约束，泛型方法就变成了

public static T GetResource<T>(string identity) where T : Resource {
    // get resource from system API

    // and then return T somehow?
    return (T) Activator.CreateInstance(typeof(T), resourceObject);
}

并使用

Person person = GetResource<Person>("person_identity");