Metadata

Sometimes it's useful to resolve metadata along with your dependency, Grace provides a Meta<T> class. The following data is provided as part of the Metadata property

• Type that is being activated
• Types that this strategy is exported as (including keyed interfaces)
• Dictionary of metadata items

Below are two unit tests that illustrate how to use metadata

[Fact]
public void Meta_Matches()
{
   var container = new DependencyInjectionContainer();

   container.Configure(
       c => c.Export<BasicService>().As<IBasicService>().WithMetadata("Hello", "World"));

   var meta = container.Locate<Meta<IBasicService>>();

   Assert.NotNull(meta);
   Assert.True(meta.Metadata.MetadataMatches("Hello", "World"));
}
       
[Fact]
public void Meta_Enumerable()
{
   var container = new DependencyInjectionContainer();

   container.Configure(c =>
   {
      c.Export<MultipleService1>().As<IMultipleService>().WithMetadata("Key", 1);
      c.Export<MultipleService2>().As<IMultipleService>().WithMetadata("Key", 2);
      c.Export<MultipleService3>().As<IMultipleService>().WithMetadata("Key", 3);
      c.Export<MultipleService4>().As<IMultipleService>().WithMetadata("Key", 4);
      c.Export<MultipleService5>().As<IMultipleService>().WithMetadata("Key", 5);
   });

   var multipleServices = 
         container.Locate<IEnumerable<Meta<IMultipleService>>>().ToArray();
            
   Assert.Equal(5, multipleServices.Length);

   Assert.Equal(1, multipleServices[0].Metadata["Key"]);
   Assert.IsType<MultipleService1>(multipleServices[0].Value);

   Assert.Equal(2, multipleServices[1].Metadata["Key"]);
   Assert.IsType<MultipleService2>(multipleServices[1].Value);

   Assert.Equal(3, multipleServices[2].Metadata["Key"]);
   Assert.IsType<MultipleService3>(multipleServices[2].Value);

   Assert.Equal(4, multipleServices[3].Metadata["Key"]);
   Assert.IsType<MultipleService4>(multipleServices[3].Value);

   Assert.Equal(5, multipleServices[4].Metadata["Key"]);
   Assert.IsType<MultipleService5>(multipleServices[4].Value);
}