Smalltalk and IoC

Question

I see a lot of IoC frameworks for .Net and Java. Does anyone know why there are no equivalent frameworks for Smalltalk. This is more a philosophy question than anything else. I'm wondering if there is something in the Smalltalk way of doing things that precludes the necessity of having an IoC framework.

Answer 1

MVC was invented on Smalltalk and is arguably the original Inversion of Control framework. While somewhat more lightweight than its java counterparts, it has the basic concepts of a model holding the data, a view rendering the data in response to events propogated from a controller.

Less flippantly, Java is actually needs a lot of framework support to do a web application without excessive quantities of boilerplate code. Smalltalk supports programming idioms such as continuations, which allow an author to pretend they are not really writing event driven code. Seaside works like this, giving the benefits of IoC with a somewhat more flexible development paradigm.

EDIT: MVC is a framework for UI's in Smalltalk (arguably it's not really a framework as such, but the class library has built in support for it). It has the inversion of control property in that the view and model respond to events dispatched by the controller - the don't call us, we'll call you property. Inversion of Control is a design pattern within frameworks that's used to reduce the need for extensive boilerplate in java applications. In some definitions of an application framework, Inversion of Control is the main property that is viewed as distinguishing a framework from a library.

Answer 2

Functions are first class citizens in smalltalk, so it is easy to have IoC without a framework.

Answer 3

I think that IOC or the Dependency Injection pattern solves a problem that doesn't really exist in the Smalltalk environment. Smalltalk is an untyped dynamic language and uses message passing to communicate. This makes for objects that are loosely coupled by nature at the language level. Any object can send a message to another object without regard to the type as long as it can process the message. So, as you might guess changing dependencies at any given time is relatively easy and natural. Just have to decide where, when, and how you want to change the dependency.