Create Nuget Packge Suppots Dependecy Injection and use Interface to be implemented

Question

I am trying to create a weather Nuget package that can be used in any .net core project, the library should give me the current weather for a specific city that I chose in Celsius or Fahrenheit.

I will use the weatherapi.com to get the current weather.

The library should support the dependency injection (DI) throw a service called IGetCurrentWeather with one method that’s take a city name and optional parameter to chose whether I want the result in Celsius or Fahrenheit.

I should be able to register the library in the startup of any .NET CORE project and provide the necessary configurations like the Code below

builder.Services.AddWeatherApi(WeatherOptions=>
WeatherOptions.ApiKey= "d1398cba8a894feb9f7180821232602");

the interface (the apikey below is for example):

public interface IGetCurrentWeather
    {
        public async Task<string> GetCurrentWeather()
        {
            HttpClient client = new HttpClient();
            HttpResponseMessage response = await client.GetAsync("http://api.weatherapi.com/v1/current.json?key=d1398cba8a894feb9f7180821232602&q=London&aqi=no\r\n");
            response.EnsureSuccessStatusCode();
            string responseBody = await response.Content.ReadAsStringAsync();

            return responseBody;
        }
    }

AddWeather Function:

public static class WeatherApi
    {
        public static WeatherOptions Options { get; } //set only via Secret Manager
        public static IServiceCollection AddWeatherApi(this IServiceCollection services, Action<WeatherOptions> configure)
        {
            services.Configure(configure) ;


            return services;

        }

WeatherOptions:

public class WeatherOptions
    {
        public string ApiKey { get; set; }
    }

how can i use the ApiKey that i entered in startup.cs when call GetCurrentWeather() function to access weatherapi.com account? Any help highly appreciated.

Answer 1

Your attempted solution here is close. But in general, you should not put an actual implementation in an interface. You can think of an interface as a contract, it defines the operations that you expect any implementing class to be able to perform.

You start off okay with this:

builder.Services.AddWeatherApi(WeatherApiOptions =>
    WeatherOptions.ApiKey= "d1398cba8a894feb9f7180821232602");

We should rename your interface, just for consistency's sake. And remove the implementation. So what you used to call IGetCurrentWeather should look like this:

public interface IWeatherApi
{
    public Task<string> GetCurrentWeather();
}

Then you need a class that implements the interface. It should receive the WeatherApiOptions via constructor injection:

public class WeatherApi : IWeatherApi
{
    readonly WeatherApiOptions _weatherApiOptions;

    public WeatherApi(IOptions<WeatherApiOptions> weatherApiOptions)
    {
        _weatherApiOptions = weatherApiOptions.Value;
    }

    public async Task<string> GetCurrentWeather()
    {
        HttpClient client = new HttpClient();
        HttpResponseMessage response = await client.GetAsync($"http://api.weatherapi.com/v1/current.json?key={_weatherApiOptions.ApiKey}&q=London&aqi=no\r\n");
        response.EnsureSuccessStatusCode();
        string responseBody = await response.Content.ReadAsStringAsync();

        return responseBody;
    }
}

Then, an extension method that helps wire up your class with the DI container. Notice that I renamed it to better describe what its purpose is

public static class WeatherApiDependencyInjectionExtensions
{
    public static IServiceCollection AddWeatherApi(this IServiceCollection services, Action<WeatherApiOptions> configure)
    {
        services.AddTransient<IWeatherApi, WeatherApi>();
        services.Configure(configure) ;
        return services;
    }
}

And rename your options class to make it clearer what its for:

public class WeatherApiOptions
{
    public string ApiKey { get; set; }
}

Also, I noticed you're using HttpClient directly. There's some downfalls associated with that. I recommend using Flurl instead.