Recommended IOC Container?

[Mike_Ward]

New to Vala. Is there a recommended IOC Container for use in desktop apps.

[nielsdg (Niels De Graef)]

Forgive me if I make some mistakes here, since it’s been almost a decade since I last had anything to with code that dealt with IOC containers.

As far as I know, GObject doesn’t really have a IOC container, but thanks to the GObject type system, it should be relatively straightforward to make something yourself. There are 2 concepts you will need here:

• a GLib.Type (in C: GType) which you can instantiate (so no abstract class). This is also the return value of the typeof() function.
• the generic way of making objects GLib.Object.new() (in C: g_object_new()), which takes such as Type as its first parameter

For example, assume that you have 2 interfaces Foo and Bar, which have an implementing class: FooImpl and BarImpl. You can make a factory class like this: (warning: I haven’t tried running this)

public class ObjectFactory : Object {

    // Save the types into a variable.
    // Option 1. Provide the types of the impls here
    private Type foo_type = typeof(FooImpl);
    private Type bar_type = typeof(BarImpl);

    // Option 2. You can make a constructor to pass on the types
    // instead of creating them by default
    // public  ObjectFactory(Type foo_type, Type bar_type) {
    //     this.foo_type = foo_type;
    //     this.bar_type = bar_type;
    // }

    /**
     * Creates an instance of {@link Foo}.
     */
    public Foo createFooInstance() {
        return (Foo) Object.new(this.foo_type);
    }

    /**
     * Creates an instance of {@link Bar}.
     * 
     * We assume that Bar has a construct property `name`,
     * to show how to pass on extra parameters.
     */
    public Bar createBarInstance(string name) {
        return (Bar) Object.new(bar_type, "name", name);
    }
}