CODEWITHSUNDEEP
.netinversion-of-controlstructuremapstructuremap3
Arghya C
Arghya C

Reputation: 10078

How to tell StructureMap 3 to use specific constructor for specific type?

I am using StructureMap (version 3.1.4.143) for general dependency resolution in my Web API project, and it's working fine so far. I want structuremap to follow it's default behavior of selecting the constructor with most parameters. However, for a specific type I want to use a specific constructor to be used.

e.g. I have some service contract

public interface IService 
{
    void DoSomething();
}

and implementation like 

public class Service : IService 
{
    public Service() { //something }
    public Service(IRepo repo, ILogger logger) { //something }
    //rest of the logic
}

For this type only, I want to use the parameter-less constructor. How do I do that in StructureMap 3 ? (I could do that to all types by creating an instance of IConstructorSelector and applying that as policy like below)

x.Policies.ConstructorSelector<ParamLessConstructorSelector>();

Upvotes: 3

Views: 654

Answers (2)

Arghya C
Arghya C

Reputation: 10078

Answering my own question:

This is the right way to do that in StructureMap 3. With SelectConstructor, structuremap infers the constructor from the given expression.

x.ForConcreteType<Service>().Configure.SelectConstructor(() => new Service());

Or, it can be specified with For-Use-mapping.

x.For<IService>().Use<Service>().SelectConstructor(() => new Service());

Check the documentation in Github StructureMap docs.

If this rule needs to applied throughout the application, the rule can be applied as a policy by creating an instance of IConstructorSelector

public class ParamLessConstructorSelector : IConstructorSelector
{
    public ConstructorInfo Find(Type pluggedType)
    {
        return pluggedType.GetConstructors().First(x => x.GetParameters().Count() == 0);
    }
}

and configuring the container.

x.Policies.ConstructorSelector<ParamLessConstructorSelector>();

Upvotes: 4

asfaloth.arwen
asfaloth.arwen

Reputation: 126

You can specify which constructor to use for a specific type. Somewhere along the lines of: 

x.SelectConstructor<Service>(() => new Service());

See the documentation for more information.

Edit:

For StructureMap3 it would be:

x.Policies.ConstructorSelector(...)

Upvotes: 0

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