Proxies are a powerful approach to implement meta-objects in object-oriented languages without having to resort to metacircular interpretation. We introduce such a meta-level API based on proxies for Javascript. We simultaneously introduce a set of design principles that characterize such APIs in general, and compare similar APIs of other languages in terms of these principles. We highlight how principled proxy-based APIs improve code robustness by avoiding interference between base and meta-level code that occur in more common reflective intercession mechanisms. Categories and Subject Descriptors D.3.2 [Language Classifications]: Object-oriented languages

Tribal Ownership unifies class nesting and object ownership. Tribal Ownership is based on Tribe, a language with nested classes and object families. In Tribal Ownership, a program’s runtime object ownership structure is characterised by the lexical nesting structure of its classes. We build on a variant of Tribe to present a descriptive ownership system, using object nesting to describe heap partitions, but without imposing any restrictions on programming disciplines. We then demonstrate how a range of different prescriptive ownership policies can be supported on top of the descriptive Tribal Ownership mechanism; including a novel owners-as-local-dominators policy. We formalise our type system and prove soundness and several ownership invariants. The resulting system requires strikingly few annotations, and uses well-understood encapsulation techniques to create ownership systems that should be intuitive for programmers.

Abstract. Unit testing is often made more difficult by the heavy use of classes as namespaces and the proliferation of static methods to encapsulate configuration code. We have analyzed the use of 120 static methods from 96 projects by categorizing them according to their responsibilities. We find that most static methods support a hodgepodge of mixed responsibilities, held together only by their common need to be globally visible. Tight coupling between instances and their classes breaks encapsulation, and, together with the global visibility of static methods, complicates testing. By making dependency injection a feature of the programming language, we can get rid of static methods altogether. We employ the following semantic changes: (1) Replace every occurrence of a global with an access to an instance variable; (2) Let that instance variable be automatically injected into the object when it is instantiated. We present Seuss, a prototype that implements this change of semantics in Smalltalk. We show how Seuss eliminates the need to use class methods for non-reflective purposes, reduces the need for creational design patterns such as Abstract Factory and simplifies configuration code, particularly for unit tests. 1

Reuse in object-oriented languages typically focuses on inheritance. Numerous techniques have been developed to provide finer-grained reuse of methods, such as flavors, mixins and traits. These techniques, however, only deal with reuse at the level of classes. Class-based reuse is inherently static. Increasing use of reflection and meta-programming techniques in real world applications underline the need for more dynamic approaches. New approaches have shifted to object-specific reuse. However, these techniques fail to provide a complete solution to the composition issues arising during reuse. We propose a new approach that deals with reuse at the object level and that supports behavioral composition. We introduce a new abstraction called a talent which models features that are shared between objects of different class hierarchies. Talents provide a composition mechanism that is as flexible as that of traits but which is dynamic. 1.