Manual registration

The [JoltExternalMethod] attribute hides the registration step. To register methods yourself, use the MethodRegistration class. It wraps everything the transformer needs to know to call your method, for both static and instance methods.

Registering the methods from external methods:

var staticRegistration = MethodRegistration.FromStaticMethod(typeof(TransformerMethods), nameof(TransformerMethods.IsNotNull));
var instanceRegistration = MethodRegistration.FromInstanceMethod(nameof(TransformerMethods.ReverseString));

An instance registration only needs the method name, not a type. The transformer resolves it against whatever method context instance you supply when creating the transformer.

Pass the registrations, plus an instance if you have instance methods:

var transformer = JoltJsonTransformer.DefaultWith(
    transformerJson,
    new[] { staticRegistration, instanceRegistration },
    new TransformerMethods());

Call Transform with your source document as usual.