Dependency Injection 觀摩筆記 (DI & IOC)

2023-12-10

觀摩 Blazored/LocalStorage 關於 Interface 設計與 Dependency Injection 的使用方式，從真實案例學習使用 Dependency Injection 🙂

說明

GitHub

// Program.cs 🐧

builder.Services.AddBlazoredLocalStorageAsSingleton();

public static IServiceCollection AddBlazoredLocalStorage
services.TryAddScoped<IStorageProvider, BrowserStorageProvider>();
services.TryAddScoped<ILocalStorageService, LocalStorageService>();

// BrowserStorageProvider.cs 🐧

public BrowserStorageProvider(IJSRuntime jSRuntime)
{
    _jSRuntime = jSRuntime;
    _jSInProcessRuntime = jSRuntime as IJSInProcessRuntime;
}

await _jSRuntime.InvokeVoidAsync("localStorage.clear", cancellationToken);

// LocalStorageService.cs 🐧

public LocalStorageService(IStorageProvider storageProvider, IJsonSerializer serializer)
{
    _storageProvider = storageProvider;
    _serializer = serializer;
}

當你註冊 services.TryAddScoped<ILocalStorageService, LocalStorageService>(); 時，ASP.NET Core 的依賴注入容器會自動查找已經註冊的依賴並將它們注入到 LocalStorageService 的實例中。容器會檢查 LocalStorageService 的建構子，並根據建構子參數的類型自動解析已經註冊的相應服務。

所以，如果你之前已經註冊了 IStorageProvider 和 IJsonSerializer 的實現類型，而這些實現類型已經被註冊為 Scoped 服務，那麼當你註冊 ILocalStorageService 時，容器將自動查找這些依賴並注入到 LocalStorageService 的實例中。