jastrachan | 14 Jul 17:05 2004

Re: use special syntax for method pointers?

On 14 Jul 2004, at 12:58, Wilson, Greg wrote:
> Hi James.  I vote for solving the problem by requiring the
> parentheses, even when there are no arguments (if for no
> other reason than the Principle of Least Surprise).

Whether we use mandatory or optional parenthesis isn't really the point 
of this thread :). I think I explained it badly, I'll try once more...

e.g. imagine if we forced mandatory parenthesis on methods with no 
arguments (which we currently do)...


works but the user's working with properties and does


now rather than getting null as there's no property called 'size', we 
get a size closure which when we call it, we get the actual size. But I 
think most of the time thats not what the user wanted - returning null 
would be less surprising. (In fact I think the least surprising thing 
to do is treat the size() method and size property as the same thing, 
but lets not go there in this thread).

If a user does


and the bean property "bar" does not exist, there may be a method of 
the same name, in which case today they'd get a method pointer instead. 
I've seen this happen a few times with users and they tend to get 
confused, because the thing they get back is a closure which isn't the 
value of the property they thought they were gonna get & they end up 
scratching their heads. This is especially true if users do things like


and they get some cryptic message about a closure not having a property 
'something' etc.

So I'm thinking, accessing bean properties & walking through object 
graphs using properties is really, really common. We do it all the time 
& its easy for us to make a typeo or use a bean property when something 
really happens to also be a method. its quite a rare thing to do to 
grab a method pointer, so why not make it slightly hard to get a method 
pointer to avoid confusing users in the common case - method pointers 
are useful, but they are an uncommon use case - so I wanted to try make 
the common use case simpler & more obvious & less surprising at the 
cost of a slightly more verbose syntax to get a method pointer.

Does that help clear it up? Whether we use mandatory parenthesis on 
methods with no arguments or not, we still have this issue I think. The 
issue really is about confusion between method pointers and bean 
properties and making the syntax to 'create a reference to an objects 
method'  should maybe be more explicit to avoid confusion? In C/C++ the 
& is used to create a pointer to something hence my thinking of


though we could always have some new method