Re: Kinds of methods

In article <8sfUf.136$B_1.119@edtnps89>,
"Oliver Wong" <owong@xxxxxxxxxxxxxx> wrote:

"Daniel T." <postmaster@xxxxxxxxxxxxx> wrote in message
news:postmaster-6FCD75.09250822032006@xxxxxxxxxxxxxxxxxxxxxxxxxx
I just wrote this up for someone on one of the C++ newsgroups. Any
comments?

Member-functions can be categorized into one of 4 types:

modifier - a member-function that can change the external state of the
object. IE calling a modifier could cause one or more other
member-functions of the object's class to behave differently or
produce different output when called on this object, than they
otherwise would before the modifier was called.

producer - a member-function that creates an object for the caller to
use, or sets the state of an object the caller passed in.

accessor - a member-function that gives the caller a pointer/reference
to one of the object's member-variables such that modifying the value
contained in the pointer/reference will change the state of the
object as if a modifier was called.

provider - a member-function that gives to the caller a
pointer/reference to one of the object's member-variables such that
modifying the value contained in the pointer/reference will not
change the state of the object that the member-function was called on.

If it were up to me, I'd split "producers" which create new objects from
those which mutate objects passed in.

I did not do that because methods that mutate objects passed in
generally load them up with data/state that the caller wants. The
mutated object is a substitute for a return value.

Then, I'd merge the producer which
creates new objects with the provider which returns objects.

I kept them separate because the two methods have very different
semantics. Multiple calls to a provider return the same object, whereas
a producer creates a new object for each call.

I'd probably end up with something like:

Setter
Getter
Factory
Mutator

What is the difference between a "Setter" and a "Mutator" in your
scheme? What is the difference between a "Getter" and a "Factory"?

I could see changing the name of "producer" to "factory" in my list, but
I figured that the term already has a rather strong connotation of a
member-function that returns something that must be deleted, and I
wanted to include member-functions that return by value.


But then there are functions which just return a value based on its inputs,
without setting, getting, making, or mutating anything. E.g.

number function double(number n) {
return n * 2;
}

The above is a producer, it creates an object.

And then there are functions which produce side-effects in the system,
without affecting the objects themselves. E.g.

console.write("Hello World!");

I guess you could argue that this write() method is affecting the state of
the conceptual console (of which the console object is acting as a proxy
for), but then you'd have these "black hole setters", where you're setting
some state which you can never actually retrieve again.

I would indeed argue that, and I see no problem with "black hole
setters".


--
Magic depends on tradition and belief. It does not welcome observation,
nor does it profit by experiment. On the other hand, science is based
on experience; it is open to correction by observation and experiment.
.

Relevant Pages

  • Re: Kinds of methods
    ... modifier - a member-function that can change the external state of the ... IE calling a modifier could cause one or more other ... or sets the state of an object the caller passed in. ... accessor - a member-function that gives the caller a pointer/reference ...
    (comp.object)
  • Kinds of methods
    ... modifier - a member-function that can change the external state of the ... IE calling a modifier could cause one or more other ... or sets the state of an object the caller passed in. ... accessor - a member-function that gives the caller a pointer/reference ...
    (comp.object)
  • Re: Kinds of methods
    ... IE calling a modifier could cause one or more other member-functions of the object's class to behave differently or produce different output when called on this object, than they otherwise would before the modifier was called. ... producer - a member-function that creates an object for the caller to use, or sets the state of an object the caller passed in. ... Read Accessor: basically a synchronous getter for knowledge responsibilities. ... basically a synchronous setter for knowledge responsibilities. ...
    (comp.object)
  • Re: Kinds of methods
    ... a modifier since it never returns to the caller but does change the external ... modifier - a member-function that can change the external state of the ... accessor - a member-function that gives the caller a pointer/reference ...
    (comp.object)
  • Re: Kinds of methods
    ... modifier - a member-function that can change the external state of the ... IE calling a modifier could cause one or more other ... Destructor is different in the way of its composition. ... Constructor has an output parameter of the object's ...
    (comp.object)