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在不知道类型的情况下返回泛型对象?

factory-pattern generics c#

bschreck · 技术社区 · 7 年前

{
   "id":"1",
   "created_at":"2017-09-19T20:41:23.093Z",
   "type":"person.created",
   "object":{
      "id":"person1",
      "created_at":"2017-09-19T20:41:23.076Z",
      "updated_at":"2017-09-19T20:41:23.076Z",
      "firstname":"First",
      ...
   }
}

内部对象可以是任何对象,因此我认为这将是使用泛型的绝佳机会,并按如下方式构建了我的类:

public class WebHookModel<T> where T : class, new()
{
    [JsonProperty(PropertyName = "id")]
    public string Id { get; set; }

    [JsonProperty(PropertyName = "created_at")]
    public DateTime CreatedAt { get; set; }

    [JsonProperty(PropertyName = "type")]
    public string Type { get; set; }

    [JsonProperty(PropertyName = "object")]
    public T Object { get; set; }

    [JsonIgnore]
    public string WebHookAction
    {
        get
        {
            return string.IsNullOrEmpty(Type) ? string.Empty : Type.Split('.').Last();
        }
    }
}

然后创建以下界面:

public interface IWebHookModelFactory<T> where T : class, new()
{
   WebHookModel<T> GetWebHookModel(string type, string jsonPayload);
}

我没有理解的是,在编译时不知道类型是什么的情况下,我应该如何实现工厂类?

稍微玩弄一下模型,我将其更改为带有抽象T对象的抽象类,以便它可以由派生类定义。

public abstract class WebHookModel<T> where T : class, new()
{
    [JsonProperty(PropertyName = "id")]
    public string Id { get; set; }

    [JsonProperty(PropertyName = "created_at")]
    public DateTime CreatedAt { get; set; }

    [JsonProperty(PropertyName = "type")]
    public string Type { get; set; }

    [JsonProperty(PropertyName = "object")]
    public abstract T Object { get; set; }

    [JsonIgnore]
    public string WebHookAction
    {
        get
        {
            return string.IsNullOrEmpty(Type) ? string.Empty : Type.Split('.').Last();
        }
    }
}

public PersonWebHookModel : WebHookModel<Person>
{
    public override Person Object { get; set; }
}

案例陈述?

public interface IWebHookFactory<TModel, TJsonObject> 
    where TJsonObject : class, new()
    where TModel : WebHookModel<TJsonObject>
{
    TModel GetWebHookModel(string type, string jsonPayload);
}

public interface IWebHookService<TModel, TJsonObject>
    where TJsonObject : class, new()
    where TModel : WebHookModel<TJsonObject>
{
    void CompleteAction(TModel webHookModel);
}

public abstract class BaseWebhookService<TModel, TJsonObject> : IWebHookService<TModel, TJsonObject>
        where TJsonObject : class, new()
        where TModel : WebHookModel<TJsonObject>
{
    public void CompleteAction(TModel webHookModel)
    {
        var self = this.GetType();
        var bitWise = System.Reflection.BindingFlags.IgnoreCase
                        | System.Reflection.BindingFlags.Instance
                        | System.Reflection.BindingFlags.NonPublic;

        var methodToCall = self.GetMethod(jsonObject.WebHookAction, bitWise);
        methodToCall.Invoke(this, new[] { jsonObject });
    }

    protected abstract void Created(TModel webHookObject);

    protected abstract void Updated(TModel webHookObject);

    protected abstract void Destroyed(TModel webHookObject);
}

public class PersonWebHookService : BaseWebHookService<PersonWebHookModel, Person>
{
    protected override void Created(PersonWebHookModel webHookModel)
    {
        throw new NotImplementedException();
    }

    protected override void Updated(PersonWebHookModel webHookModel)
    {
        throw new NotImplementedException();
    }

    protected override void Destroyed(PersonWebHookModel webHookModel)
    {
        throw new NotImplementedException();
    }
}

1 回复 | 直到 7 年前

Mike S 7 年前

解决方案的要点: 2.不知何故,您需要从JSON负载中的类型标记映射到实际的C#类。
即,“person.created”,“-->“person”。
如果控制序列化格式,则为JSON。Net可以插入自己的类型标记,并为您执行此操作。假设你不能走那条路。。。因此,您需要像字典这样的东西来包含映射。

abstract class WebhookPayload // Note this base class is not generic! 
{
    // Common base properties here 

    public abstract void DoWork();
}

abstract class PersonPayload : WebhookPayload
{
    public override void DoWork()
    {
        // your derived impl here 
    }
}

    static Dictionary<string, Type> _map = new Dictionary<string, Type>
    {
        { "person.created", typeof(PersonPayload)}
    }; // Add more entries here 

    public static WebhookPayload Deserialize(string json)
    {
        // 1. only parse once!
        var jobj = JObject.Parse(json); 

        // 2. get the c# type 
        var strType = jobj["type"].ToString(); 

        Type type;
        if (!_map.TryGetValue(strType, out type))
        {
            // Error! Unrecognized type
        }

        // 3. Now deserialize 
        var obj = (WebhookPayload) jobj.ToObject(type);
        return obj;
    }