As i'm trying to build some kind of context oriented mechanism, i have the same need of behavior modification for a single instance of a class. I use virus-proxies in Ghost, that can intercept a message upon its reception in a particular object. From there it is possible to choose the code you want to run, being the original method or an other implementation. It works pretty well (by the way i still need to thanks the person here that recommended Ghost to me...).
However you still need to store your behaviors implementations somewhere, in classes or blocks stored in variables... Le 2016-07-24 17:14, Eric Velten de Melo a écrit : > Actually I wanted to have many different object instances with different > behaviours picked at random from a list of available behaviours, but didn't > find practical to create a class for each different method implementation and > delegating to it, since there are many, possibly unlimited valid behaviours. > > So maybe changing method implementation at runtime is not what I want because > the method implementation will be shared among all instances. What I had in > mind was a functionality similar to prototyped languages like Self and > Javascript in which you could change the behaviour inside the object and not > the class/prototype. > > 2016-07-23 7:35 GMT-03:00 Norbert Hartl <norb...@hartl.name>: > >> Can you elaborate on the reason why want to modify behaviour? And how you >> would like it to happen? >> If the code you want to modify is your own code than you can solve that most >> of time with the things you already have. Your example using a block might >> be altered to be a strategy pattern. That means you keep one ore more >> instance variables for strategy objects. Then you delegate parts of your >> behaviour to those objects. You can based on context exchange those objects >> to adjust behaviour. >> If it is not feasible to change the internal state of an object but you know >> all possible variants you can implement all variations as methods in the >> object. The right method can be invoked by doing a double dispatch with >> another object providing contextual information. >> There are plenty of possibilities so you need to know what is the context >> that is responsible for switching behaviour and the requirements of the >> behaviour modifications. Can you alter the object? Is the number of >> modifications a fixed number? Does the modification need to be thread safe? >> >> Norbert >> >>> Am 23.07.2016 um 00:41 schrieb Eric Velten de Melo <ericvm...@gmail.com>: >>> >>> Hello, >>> >>> One thing I try to do often is changing the behaviour of a method >>> dynamically at runtime. The current way I do this is by having a block as >>> an instance variable and having the method call this block, but I find this >>> approach a bit cumbersome. Is there some other way or is this the >>> recommended approach? >>> >>> I mean, I suppose methods could be changed dynamically by means of >>> reflection somehow, but is this an easy or recommended way of programming >>> in Smalltalk? Should slots make things easier? >>> >>> Eric -- kloum.io
