Yehuda Katz (ph) 718.877.1325
On Tue, Oct 16, 2012 at 5:43 PM, Allen Wirfs-Brock <[email protected]>wrote: > > On Oct 16, 2012, at 2:36 PM, Tab Atkins Jr. wrote: > > > On Tue, Oct 16, 2012 at 2:24 PM, Allen Wirfs-Brock > >> > >> You might not agree with the above guideline, or choose to follow it. > >> That's fine. But, what you you propose as an alternative. What are > your > >> guidelines for choosing to use an accessor rather than a method? If > you > >> consider you example to be a reflection of "good design" what are the > >> specific design principles it is following. Why is that an appropriate > >> place to use an accessor. > > > > I consider Yehuda's example to be a perfectly fine and completely > > normal place to use an accessor. *Accessing* the list of comments > > attached to a post is conceptually a side-effect-free operation. > > While it can change over time, it only does so due to obvious actions > > - querying it twice, one immediately after the other, *will* give === > > results. > > > > *Setting* the attribute may have side-effects, but reasonable ones > > (setting/unsetting Comments.post or Post.comments on other objects). > > This is a reasonable thing for a setter to do. > > > > I don't see any reason to make these two into methods. > > So, what are the design guidelines that you would apply leads to these > being accessors? When do you use a method? When do you use an accessor? > One possible approach would be to have clear design guidelines for *getters*, and allow setters with reasonable observable side-effects for getters that comply. That is the approach I use in my designs. > > Allen > > > >
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