Added support for multiple constructors and best match greedy resolution.

.gitea/workflows/nuget-pkg-build.yml

@@ -21,6 +21,6 @@ jobs:
       #- name: Test
       #  run: dotnet test -c Release --no-build
       - name: Pack nugets
-        run: dotnet pack Syrette -c Release --no-build --output .
+        run: dotnet pack Syrette -c Release --no-build --output . --include-symbols --include-source
       - name: Push to NuGet
         run: dotnet nuget push "*.nupkg" --api-key ${{secrets.NUGETAPIKEY}} --source https://api.nuget.org/v3/index.json

DISandbox/Program.cs

@@ -21,8 +21,23 @@ interface IOtherService {
 class GuidService : IOtherService {
     public Guid Id { get; } = Guid.NewGuid();
 }
+public interface INotRegisteredService {
+    void DoSomething();
+}
+
+class GuidDependantService {
+    private readonly IService logService;
+    private readonly IOtherService? guidService;
+
+    public GuidDependantService(IService logService, INotRegisteredService guidService) {
+        this.logService = logService;
+    }
+
+    public GuidDependantService(IService logService, IOtherService guidService) {
+        this.logService = logService;
+        this.guidService = guidService;
+    }
 
-class GuidDependantService(IService logService, IOtherService guidService) {
     public void LogWithId(string message) {
         logService.Log($"[GuidDependantService] {message} (ID: {guidService.Id})");
     }

README.md

@@ -10,11 +10,11 @@ It is designed to be used in minimalistic applications, such as console applicat
 - **Lightweight**: Minimal codebase with no external dependencies. 1 class, the service container. You don't need anything else.
 - **Simple API**: You register services using two methods (one for singletons, one for transients) and resolve them with one.
 - **Supports Singleton and Transient lifetimes**: Choose between singleton (one instance per container) and transient (new instance per resolution) lifetimes for your services.
+- **Greedy matching constructor selection**: When resolving a service, the constructor with the most parameters that can be satisfied by the container is chosen.
 
 ## Limitations
 - **No support for scoped lifetimes**
 - **No support for property injection or method injection.**
-- **Every service should have only 1 constructor.** (planned to be lifted in future versions)
 
 ## Usage
 ````csharp

Syrette/ServiceContainer.cs

@@ -1,4 +1,6 @@
-namespace Syrette;
+using System.Reflection;
+
+namespace Syrette;
 
 /// <summary>
 /// Container for managing service registrations and resolutions.
@@ -26,9 +28,7 @@ public class ServiceContainer {
         descriptors.Add(new ServiceDescriptor {
             ServiceType = typeof(TInterface),
             ImplementationType = typeof(TImplementation),
-            Lifetime = ServiceLifetime.Lifetime,
-            RequiredTypes = typeof(TImplementation).GetConstructors().Single()
-                .GetParameters().Select(p => p.ParameterType).ToList()
+            Lifetime = ServiceLifetime.Lifetime
         });
         return this;
     }
@@ -43,9 +43,7 @@ public class ServiceContainer {
         descriptors.Add(new ServiceDescriptor {
             ServiceType = typeof(TInterface),
             ImplementationType = typeof(TImplementation),
-            Lifetime = ServiceLifetime.Transient,
-            RequiredTypes = typeof(TImplementation).GetConstructors().Single()
-                .GetParameters().Select(p => p.ParameterType).ToList()
+            Lifetime = ServiceLifetime.Transient
         });
         return this;
     }
@@ -71,20 +69,27 @@ public class ServiceContainer {
         
         if (descriptor == null) throw new Exception($"Service of type {typeof(TInterface)} not registered.");
         
-        // Ensure all required dependencies are registered
-        //TODO: some services might be asking for specific implementations, not interfaces. We should check for that too.
-        var missing = descriptor.RequiredTypes
-            //filter all required types that are not in the registered descriptors
-            .Where(t => descriptors.All(d => d.ServiceType != t))
-            .Select(t => t.Name)
-            .ToList();
+        var ctors = descriptor.ImplementationType.GetConstructors();
+        int max = -1;
+        ConstructorInfo? bestCtor = null;
         
-        if (missing.Any())
-            throw new Exception($"Cannot create service of type {typeof(TInterface)}. Missing dependencies: {string.Join(", ", missing)}");
+        foreach (var ctor in ctors) {
+            var parameters = ctor.GetParameters();
+            //check if all parameters are registered services or optional
+            if (!parameters.All(p => descriptors.Any(d => d.ServiceType == p.ParameterType) || p.IsOptional)) continue;
+            //check if this constructor has more registered parameters than the previous best
+            int satisfiedParams = parameters.Count(p => descriptors.Any(d => d.ServiceType == p.ParameterType));
+            if (satisfiedParams > max) {
+                max = satisfiedParams;
+                bestCtor = ctor;
+            }
+        }
+        if (bestCtor == null)
+            throw new Exception($"Cannot create service of type {typeof(TInterface)}. No suitable constructor found.");
         
         // Transient: create a new instance each time
         if (descriptor.Lifetime != ServiceLifetime.Lifetime) {
-            var service = Instantiate<TInterface>(descriptor);
+            var service = Instantiate<TInterface>(descriptor, bestCtor);
             return service;
         }
 
@@ -97,12 +102,22 @@ public class ServiceContainer {
         return newSingleton;
     }
 
-    private TInterface Instantiate<TInterface>(ServiceDescriptor descriptor) {
-        var par = descriptor.ImplementationType
-            .GetConstructors().Single()
-            .GetParameters()
-            .Select(p => p.ParameterType)
-            .ToList();
+    private TInterface Instantiate<TInterface>(ServiceDescriptor descriptor, ConstructorInfo? ctor = null) {
+        if (ctor == null && descriptor.ImplementationType.GetConstructors().Length > 1)
+            throw new Exception($"Multiple constructors found for type {descriptor.ImplementationType}. Please provide a specific constructor.");
+        
+        List<Type> par;
+        
+        if (ctor == null)
+            par = descriptor.ImplementationType
+                .GetConstructors().Single()
+                .GetParameters()
+                .Select(p => p.ParameterType)
+                .ToList();
+        else 
+            par = ctor.GetParameters()
+                .Select(p => p.ParameterType)
+                .ToList();
         
         object[] parameters = new object[par.Count];
         

Syrette/ServiceDescriptor.cs

@@ -19,9 +19,4 @@ public class ServiceDescriptor
     /// Gets or sets the lifetime of the service (e.g., Singleton or Transient).
     /// </summary>
     public required ServiceLifetime Lifetime { get; set; }
-
-    /// <summary>
-    /// Gets or sets the list of types required by the implementation (dependencies).
-    /// </summary>
-    public List<Type> RequiredTypes { get; set; } = new();
 }

Syrette/Syrette.csproj

@@ -6,11 +6,10 @@
         </Content>
     </ItemGroup>
     <PropertyGroup>
-        <TargetFramework>net9.0</TargetFramework>
         <LangVersion>latest</LangVersion>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
-        <Version>0.0.1.1-alpha</Version>
+        <Version>0.0.1.2-alpha</Version>
         <Title>Syrette </Title>
         <Authors>Lorefice Samuele</Authors>
         <Description>Syrette is a minimalistic dependency injection library for C#. It aims to provide a simple and efficient way to achieve dependency injections in your applications without the overhead of larger frameworks.</Description>
@@ -24,6 +23,7 @@
         <Company>Samuele Lorefice</Company>
         <Deterministic>true</Deterministic>
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
+        <TargetFrameworks>net9.0;net8.0</TargetFrameworks>
     </PropertyGroup>
     <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
       <DebugSymbols>true</DebugSymbols>