c# - C# 中的接口(interface)和类

Question

我收到以下错误:

test.Services.JobService' does not contain a constructor that takes 0 arguments.

这是代码:

工作服务.cs:

namespace TesteUltrafan.Services
{
    public class JobService
    {
        private readonly IRepository _repository;

        public JobService(IRepository repository)
        {
            _repository = repository;
        }

        public Job CreateJobBanker()
        {
            var banker = new Job();

            string id = Guid.NewGuid().ToString("N");

            Console.WriteLine("Novo job banker id: {0}", id);

            banker.Id = id;
            banker.Type = JobType.Banker;
            banker.CreatedAt = DateTime.Now;

            Console.WriteLine("Salvando job banker id: {0}", id);

            Job jobBanker = _repository.SaveJob(banker);

            return jobBanker;
        }
    }
}

程序.cs:

public class Program
{
    public static void Main()
    {
        var jobService = new JobService(); <---- Here is the error.

        Console.WriteLine("Creating job banker, creation:");

        Job jobBanker = jobService.CreateJobBanker();

        Console.WriteLine("Job banker: {0}", jobBanker);
    }
}

工作.cs:

public class Job
{
    public string Id { get; set; }
    public DateTime CreatedAt { get; set; }
    public JobType Type { get; set; }
}

工作类型.cs:

public enum JobType
{
    Actor = 1,
    Agricultural = 2,
    Banker = 3,
    EngineerCivil = 4,
    Another = 5,
}

Answer 1

您要么需要在您的 JobService 类中创建一个无参数构造函数(我不会这样做，因为那样您的类将无法正常工作 - 将不会引用任何存储库)或者最好传递一个Repository 实例作为构造此实例时的参数。

所以代码最好应该是这样的:

public class Program
{
    public static void Main()
    {
        var jobService = new JobService(new Repository()); 

        Console.WriteLine("Creating job banker, creation:");

        Job jobBanker = jobService.CreateJobBanker();

        Console.WriteLine("Job banker: {0}", jobBanker);
    }
}

Repository 应该是一个实现IRepository 接口(interface)的类。如果不传递此实例，您的 CreateJobBanker 将无法工作。

虽然推荐使用一些 IoC 容器，因为您的代码遵循控制反转原则(您可能甚至没有意识到这一点)。