That said, consider the following. I've got a renderer that accepts a sprite to draw.

Version 1: I pass the sprite object to the renderer, and the renderer gets the texture contained in the sprite and draws it, scaling it according to the sprite's size and position public members.

I then decide that all of my sprites draw slightly differently (different scales/glow effects/color tint/whatever).

Version 2: I pass the renderer my sprite, it gets the size and render settings members from the sprite, and then draws it.

Oops! I now decide I want a hierarchy of sprites, so that I can add hats.

Version 3: Same as version 2, but in the draw routine now the renderer asks the sprite for its parent to calculate its position and size, and now I've got more renderer code and more sprite code. I can't just use the exposed position member of the sprite--it has context and logic behind it that must be done.

Oh wait, I have a problem in which the sprite glow might change depending on how many times its been drawn.

Version 4: The renderer now has to keep track of how many times it's drawn a sprite. My renderer is getting a bit chunky now.

Did I mention scale should change according to time but also the sprite's velocity?

Version 5: Renderer grabs these variables directly, and does all that other stuff too.

...and that now I want to let that scale be overridden by a isConstantSize flag on the sprite?

Version 6: aaaaaargh

...and that now the sprite can decide it wants to defer to a parent sprite's settings sometimes?

Version 7: what did i do to deserve this?

~

Proper encapsulation and use of accessors is clearly a sign of paranoia. That said, as your code evolves, you might find that this paranoia is completely justified. Hiding queries behind interfaces lets you future-proof them and trivially add more advanced behavior and hooks.

Even when you are working by yourself on an internal project, you are never working alone. You are also working with your future self, and that person is guaranteed to want something different from you and to make assumptions that you are not.

This flexibility is not something you might think you need.

You might also never need to debug your own code, or check your assumptions about variables, or track who is accessing what when.

(for what it's worth, I don't use protection for data members of Plain-Old-Data types [say, messages or vectors] very often--they're too dumb to deserve this sort of extensibility or cost)

You replace

  public var myAttribute:int;

  public function get myAttribute():int;

This allows you to use all sort of syntactic sugar ("object.myAttribute++", "+=" and other assignments), and for dynamic languages you can get and set values just from a reference to the object and the attribute's name. This last part is invaluable for animation engines.

So add it then. Don't pre-generalize everything just in case.

This isn't premature abstraction or architecture astronautics--this is just good practice.

If you are in a language like Java or C, your compiler should optimize away the call if it doesn't do something clever.

If you are in Ruby, this is so easy to do that it doesn't even need mentioning--you just call the variable directly and behind the scenes you have replaced the variable name to be a function doing your magic instead.

If your fingers protest at the additional "get" in your function names, go and buy yourself a real IDE.

EDIT: Parent thread added clarification worth noting here. I'm not saying you should add accessors for every protected member--that's just as bad. I mean to say you should only expose members that absolutely require it (the fewer the better, generally), and only do so through function interfaces you can hook. :)

Plus, no, often I can't afford a function invokation. Because it's yet another cache miss.

If all of those things don't matter (or you work on a large enough team that the benefits of abstraction are worth it), yes, add getters/setters everywhere. For the rest of us, we might have actual _reasons_ why we don't cargo-cult our code.

This actually isn't as wildly hypothetical a situation as one might guess. At least in the Android world, "Avoid getters and setters" is on the short list of performance suggestions.

http://developer.android.com/guide/practices/design/performa...

Even if the (Java, or otherwise) IDE can generate piles of crap code, I still hate reading piles of crap code, though. Sometimes I just want a "struct" :-)

Now back to my Java work...

If you can't see how abstraction layers affect performance, go buy yourself a real education. This isn't about premature optimization, it's about not applying premature generalization.

Sometimes it immediately makes sense to add accessors. In that case I add them right away.

Sometimes there is no apparent need for accessors, so I don't add them yet. They're easy to add (you argue so vehemently yourself), why would there be a problem adding them as needed?

A blanket rule of "just add them, always" is just a crutch for mediocre developers who aren't capable or willing to actively think about what they're working on.

Conventional wisdom is there for a reason--it was wisdom hard fought over many iterations from people who came before. Conventional wisdom has won out against many competing ideas, a survival of the fittest of sorts. You may not always fully comprehend the reasoning for a particular 'best-practices' rule, but you're foolish not to follow it for that reason.

Adding accessors is not 'premature generalization', it's just how you write well engineered code.

On a more serious note, trivial accessors generally don't result in any more compiled code than direct field accesses, but do have the advantage of abstraction. If your development process is limited by the time it takes you type out the name of an accessor (or in my case, the first 3 letters), then you must be really productive or not do other things like documentation or testing.

  sprite.render(context);

You want sprites to be an array, and render that in one go.

(contrived example for making a point... visiting a draw() method with a solid renderer interface is the answer we usually use)

Suppose you have a member named "x." Someday, you might want to stop storing x, and instead make it a calculated value. At which point you'll need a method. Or, when setting x, you may someday want to increment a counter, or transform the input data, or take some other action. Again, you'll need a method.

Yes, it's very easy to add an accessor later. But then you'll most likely have to edit every line of code that accessed the now-defunct member variable. Your IDE may make this easy, but I'd still prefer not to have to do it.

That's not to say writing accessors is always the best choice. I'm just saying there can be good reasons to do it. Like all things in software engineering, there's no one-size-fits-all rule about this. Notch is right about the bloat accessors create, so you have to weight the advantages and disadvantages yourself in each case.

Then you can convert your public vars into properties at a later date.

This means that you will not have to (necessarily) rewrite your code as the language knows that

a = myobj.myvar

now should call getmyvar() in the containing class and:

myob.myvar = a

should call setmyvar(a) , I know that C# certainly allows this.

Not sure how this is implemented.

C# and Objective-C (And I assume similar languages too) can have public accessors which are not used like function. No need to add ()'s everywhere.

As far as I'm concerned it's quite far from it, because C# still allows public fields, properties and fields are incompatible, properties and methods are separate and Microsoft specifies different naming conventions for fields on one hand and properties & methods on the other.

Perfection is Smalltalk's way of doing it.

And in a syntactic line closer to ALGOL, Ruby is about as good as it gets: no public fields, "properties" are normal methods (setters have a little bit of syntactic sugar, but not much) and auto-generating a bunch of getters, setters or both is a class-level method call.

*Honest question - I first learned programming with C#, and so those conventions seem 'correct' to me.

Which is precisely one of the problems of properties in C#, it makes fields and properties look and feel extremely different from the outside which violates the uniform access principle.

As I noted, ideally C# should not have public fields in the first place.

Vector v1(v2.getX(), v2.getY(), v2.getZ()); vs Vector v1(v2.x, v2.y, v2.z);

Most software are outdated after a couple of years.

But I still think that accessors are a must if you know that the software will be immortal (like Internet banking applications)

I can't say I know the average shelf life of a software component in various languages, but I can say that at least things like Java have managed to justify their use of accessors by that metric. Maybe the focus should be on writing less throwaway code than deciding whether to "invest" a few extra minutes or not on accessors.

tl;dr; Usually enterprise Java applications does have long "service life".

You'd be surprised. Tons of code runs in production, even in the latest of shiny systems, that was written 10 and 20 and 30 years ago -- either in whole or in parts, refactored etc.

From 1986's NeXT OS that is now OS X Lion and iOS 5, to Bill Joy's TCP/IP, to Emacs.

And tons of enterprise/banking/financial/military systems use ancient code, even 70's COBOL...

This makes the code neater and enforces the abstraction--the user of the property does not need to know whether you've implemented it as a simple variable or a complicated method.

A bunch of other language let you do this as well.

Easy is an understatement. It's 2-3 clicks away in Eclipse.

But yeah, its a bunch of ridicules, generated spam.

After reading the Eiffel book and thinking about things like programming by contract and class invariants, the bean pattern which constructs empty, initially useless (or at least unreliable) objects seemed like a huge step back.

(Mime aside, do we get to hear what the argument was?)

  # Old
  class Foo(object):
      def __init__(self):
          self.x = 0
  foo = Foo()
  foo.x = 1

  # New
  class Foo(object):
      def __init__(self):
          self.__x = 0
      @property
      def x(self):
          return self.__x
      @x.setter
      def x(self, val):
          self.__x = val
          do_other_stuff()

I don't think this is true. I'll concede that it may be a requirement for certain things like an ORM API, but in the general case, it's bad practice. The mere act of adding a getter violates immutability.

Uh what? No it does not. Writing stupid getters (or classes) might, but writing getters does not "violate immutability".

Naturally, getters are not of much use if all your fields are final and hold immutable objects, but the latter can be tricky in many OO languages.

Getters significantly improve the situation there, by providing a point at which you can clone your internal state and return a copy, letting you keep your object immutable even if you have mutable fields (of course this assumes you can deeply copy all your mutable member objects)

On the other hand, you could have "setters" using the same naming convention which do a clone-and-replace (and return the new object), that would not violate immutability (and would be easier than building objects from scratch every time from the outside) e.g.

    Type setFoo(FooType foo) {
        return new Type(
            this.field0,
            this.field1,
            this.field2,
            foo, // bam
            this.field4);
    }

The intent of the comment you are replying to "best practice is if you would add a public member, instead add a private member and a setter & getter" which is generally correct.

I do agree that most modern languages have a much more elegant solution for this.

I found this worked very well in real life.

In practice, it's useful because it allows more easily for instrumentation later on. And you can easily throw a "synchronized" on the method if necessary.