• Nub Public (3/3) Jun 24 2011 Is there a way to remove all elements in an associative array?
• Jonathan M Davis (12/16) Jun 24 2011 clear invokes an object's destructor and puts it in an invalid state. Yo...
• Nub Public (6/23) Jun 24 2011 How to do this properly?
• Ali =?iso-8859-1?q?=C7ehreli?= (7/13) Jun 24 2011 The .keys property returns an array of the keys (as a copy). This should...
• Nub Public (2/15) Jun 24 2011 Thank you.
• bearophile (4/7) Jun 25 2011 I am sure there's a need for a built-in function (or function in Object)...
• Jimmy Cao (4/7) Jun 24 2011 This same thing was asked many years ago:

Nub Public <nubpublic gmail.com> writes:

Is there a way to remove all elements in an associative array?

I tried clear() but it doesn't work. For some reason it sets the length 
of the array to gibberish. What does clear() do exactly?

Jonathan M Davis <jmdavisProg gmx.com> writes:

On 2011-06-24 20:41, Nub Public wrote:
 Is there a way to remove all elements in an associative array?
 
 I tried clear() but it doesn't work. For some reason it sets the length
 of the array to gibberish. What does clear() do exactly?

clear invokes an object's destructor and puts it in an invalid state. You 
definitely don't want to do that to an associative array to empty it - if 
ever.

Generally, the simplest thing to do to clear out an AA is to simply create a 
new one. Either set the existing one to null or assign it a new AA. The old 
one can then be garbage collected. Now, if you actually need to remove all of 
the elements from the existing one (e.g. because multiple places in your code 
have references to it), then the only way that I'm aware of is to remove all 
of the elements one by one with remove.

http://www.d-programming-language.org/hash-map.html

- Jonathan M Davis

Nub Public <nubpublic gmail.com> writes:

On 6/25/2011 11:54 AM, Jonathan M Davis wrote:
 On 2011-06-24 20:41, Nub Public wrote:
 Is there a way to remove all elements in an associative array?

 I tried clear() but it doesn't work. For some reason it sets the length
 of the array to gibberish. What does clear() do exactly?

 clear invokes an object's destructor and puts it in an invalid state. You
 definitely don't want to do that to an associative array to empty it - if
 ever.

 Generally, the simplest thing to do to clear out an AA is to simply create a
 new one. Either set the existing one to null or assign it a new AA. The old
 one can then be garbage collected.

Thanks. That was very helpful.


 Now, if you actually need to remove all of
 the elements from the existing one (e.g. because multiple places in your code
 have references to it), then the only way that I'm aware of is to remove all
 of the elements one by one with remove.

 http://www.d-programming-language.org/hash-map.html

 - Jonathan M Davis

How to do this properly?

foreach (key, value; aa)
   remove(key);

This doesn't work since it's altering the aa in each iteration.

Ali =?iso-8859-1?q?=C7ehreli?= <acehreli yahoo.com> writes:

On Sat, 25 Jun 2011 12:57:15 +0800, Nub Public wrote:

 How to do this properly?
 
 foreach (key, value; aa)
    remove(key);
 
 This doesn't work since it's altering the aa in each iteration.

The .keys property returns an array of the keys (as a copy). This should 
be safe:

    foreach (key; aa.keys) {
        aa.remove(key);
    }

Ali

Nub Public <nubpublic gmail.com> writes:

On 6/25/2011 1:57 PM, Ali Çehreli wrote:
 On Sat, 25 Jun 2011 12:57:15 +0800, Nub Public wrote:

 How to do this properly?

 foreach (key, value; aa)
     remove(key);

 This doesn't work since it's altering the aa in each iteration.

 The .keys property returns an array of the keys (as a copy). This should
 be safe:

      foreach (key; aa.keys) {
          aa.remove(key);
      }

 Ali

Thank you.

bearophile <bearophileHUGS lycos.com> writes:

Jonathan M Davis:

 clear invokes an object's destructor and puts it in an invalid state. You 
 definitely don't want to do that to an associative array to empty it - if 
 ever.

I am sure there's a need for a built-in function (or function in Object) to
delete all items of an associative array. It's a basic common need.

Bye,
bearophile

Jimmy Cao <jcao219 gmail.com> writes:

On Fri, Jun 24, 2011 at 10:41 PM, Nub Public <nubpublic gmail.com> wrote:

 Is there a way to remove all elements in an associative array?

 I tried clear() but it doesn't work. For some reason it sets the length of
 the array to gibberish. What does clear() do exactly?


This same thing was asked many years ago:
http://dsource.org/projects/tutorials/wiki/DeleteAllKeysFromAssocArrayExample

The example is very old and it's for D1.