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digitalmars.D - Weak references

reply Jesper Nordenberg <jesper nnl.se> writes:
I'm new to D. Are there any equivalents of Java's WeakReference and 
SoftReference in D? What is the recommended IDE for developing in D?

/Jesper
Dec 09 2004
next sibling parent reply Sebastian Beschke <s.beschke gmx.de> writes:
Jesper Nordenberg wrote:

 What is the recommended IDE for developing in D?



Depends on who you ask :)
I'll go ahead and recommend Ant's LEDS at http://leds.sf.net/ even 
though I've never used it.
Apart from that, jEdit (http://www.jedit.org/) is doing quite OK for me, 
too :)


 
 /Jesper
Dec 09 2004
parent Ant <Ant_member pathlink.com> writes:
In article <cp9uft$o0v$1 digitaldaemon.com>, Sebastian Beschke says...

Jesper Nordenberg wrote:

 What is the recommended IDE for developing in D?



Depends on who you ask :)
I'll go ahead and recommend Ant's LEDS at http://leds.sf.net/ even 
though I've never used it.



this is the greatest compliment, no not toleds, but
to my marketing strategy until now! :)

of course it's http://leds.sourceforge.net/
(see, I never loose an opportunity to divulgate leds url!)


Apart from that, jEdit (http://www.jedit.org/) is doing quite OK for me, 
too :)



also check http://www.prowiki.org/wiki4d/wiki.cgi?EditorSupport

Ant
Dec 09 2004
prev sibling parent reply Ben Hinkle <bhinkle4 juno.com> writes:
 Are there any equivalents of Java's WeakReference and
 SoftReference in D? 



nope. I don't have any links handy but I remember it coming up on the
newsgroup before and it didn't seem likely to show up any time soon if at
all. It complicates the GC too much (or something like that) for too little
benefit.

-Ben
Dec 09 2004
next sibling parent reply Jesper Nordenberg <jesper nnl.se> writes:
Ben Hinkle wrote:

Are there any equivalents of Java's WeakReference and
SoftReference in D? 



 
 nope. I don't have any links handy but I remember it coming up on the
 newsgroup before and it didn't seem likely to show up any time soon if at
 all. It complicates the GC too much (or something like that) for too little
 benefit.



Too bad. I think weak references are very useful when creating loosely 
coupled classes.

/Jesper
Dec 10 2004
parent reply "Ben Hinkle" <ben.hinkle gmail.com> writes:
"Jesper Nordenberg" <jesper nnl.se> wrote in message 
news:cpbn88$h1u$1 digitaldaemon.com...

 Ben Hinkle wrote:

Are there any equivalents of Java's WeakReference and
SoftReference in D?




 nope. I don't have any links handy but I remember it coming up on the
 newsgroup before and it didn't seem likely to show up any time soon if at
 all. It complicates the GC too much (or something like that) for too 
 little
 benefit.



 Too bad. I think weak references are very useful when creating loosely 
 coupled classes.

 /Jesper



Can you give more details? The current design won't change without making an 
argument to change it and the argument will heavily depend on use cases and 
how hard the alternative designs are. So the more examples we have of people 
using weak references the better.
Dec 10 2004
parent reply Jesper Nordenberg <jesper nnl.se> writes:
Ben Hinkle wrote:

Too bad. I think weak references are very useful when creating loosely 
coupled classes.

/Jesper



 
 Can you give more details? The current design won't change without making an 
 argument to change it and the argument will heavily depend on use cases and 
 how hard the alternative designs are. So the more examples we have of people 
 using weak references the better.



I typically use weak references for listeners in Java. You might have an 
object A listening on another object B, but you don't want to prevent A 
from being GC'ed just because B keeps a reference to it. When there are 
no other references to A beside the one in B, you want the listener to 
be automatically removed from B. This scenario is very common in for 
example GUI applications.

Another scenario is when you want to minimize the dependencies between 
classes and thus store information about an object in a map rather than 
storing the information inside the object. When the object is GC'ed you 
want to remove the entry from the map. In Java this is easily solved by 
using a WeakHashMap which automatically removes the key-value pair from 
the map when the key is GC'ed.

Maybe there are other ways besides weak references to solve this in D.

/Jesper
Dec 10 2004
parent reply Vathix <vathix dprogramming.com> writes:
On Fri, 10 Dec 2004 16:27:17 +0100, Jesper Nordenberg <jesper nnl.se>  
wrote:


 Ben Hinkle wrote:

 Too bad. I think weak references are very useful when creating loosely  
 coupled classes.

 /Jesper



 making an argument to change it and the argument will heavily depend on  
 use cases and how hard the alternative designs are. So the more  
 examples we have of people using weak references the better.



 I typically use weak references for listeners in Java. You might have an  
 object A listening on another object B, but you don't want to prevent A  
 from being GC'ed just because B keeps a reference to it. When there are  
 no other references to A beside the one in B, you want the listener to  
 be automatically removed from B. This scenario is very common in for  
 example GUI applications.



I had to do this for a few things in DFL, like menus. I accomplished it by  
storing the reference in malloc'd memory.
Dec 10 2004
parent reply Bastiaan Veelo <Bastiaan.N.Veelo ntnu.no> writes:
Vathix wrote:

 On Fri, 10 Dec 2004 16:27:17 +0100, Jesper Nordenberg <jesper nnl.se>  
 wrote:
 

 Ben Hinkle wrote:


 Too bad. I think weak references are very useful when creating 
 loosely  coupled classes.

 /Jesper



   Can you give more details? The current design won't change without  
 making an argument to change it and the argument will heavily depend 
 on  use cases and how hard the alternative designs are. So the more  
 examples we have of people using weak references the better.




 I typically use weak references for listeners in Java. You might have 
 an  object A listening on another object B, but you don't want to 
 prevent A  from being GC'ed just because B keeps a reference to it. 
 When there are  no other references to A beside the one in B, you want 
 the listener to  be automatically removed from B. This scenario is 
 very common in for  example GUI applications.



 
 I had to do this for a few things in DFL, like menus. I accomplished it 
 by  storing the reference in malloc'd memory.



I am very interested in this. Where can I find the details?

Bastiaan.
Dec 11 2004
parent Vathix <vathix dprogramming.com> writes:
   I had to do this for a few things in DFL, like menus. I accomplished  
 it by  storing the reference in malloc'd memory.



 I am very interested in this. Where can I find the details?



Something like this. It's just an idea, it won't compile as-is:


class Item // Item you want weak references to.
{
    this()
    {
       addItem(this);
    }

    ~this()
    {
       removeItem(this);
    }
}

Item[] refItems; // malloc'd memory holding weak references to Item`s.

void addItem(Item item)
{
    refItems = realloc(refItems, count * Item.sizeof);
    refItems[i] = item;
}

void removeItem(Item item)
{
    int i;
    for(i = 0; i != refItems.length; i++)
    {
       if(item == refItems[i])
       {
          refItems = realloc(refItems, count * Item.sizeof);
          break;
       }
    }
}
Dec 11 2004
prev sibling parent Russ Lewis <spamhole-2001-07-16 deming-os.org> writes:
Ben Hinkle wrote:

Are there any equivalents of Java's WeakReference and
SoftReference in D? 



 
 nope. I don't have any links handy but I remember it coming up on the
 newsgroup before and it didn't seem likely to show up any time soon if at
 all. It complicates the GC too much (or something like that) for too little
 benefit.



It is possible to create them (without altering the GC), but it takes 
some rather arcane magic to do it.
Dec 10 2004