🔒 Locked

Epiphany (pointer comparison)

Started by jamesleighe Oct 20, 2011 at 12:31 AM 3 replies 1.2k views

Original Post

Oct 20, 2011 at 12:31 AM

So, pretty much I can sum this up in code.


 void FindThingInArray (Thing* thing)
 {
 for (uint32 i = 0; i < vector.Count (); ++i)
 {
 if (vector->GetID () == thing->GetID ())
 return i;
 }
 }

Notice in the second one, I'm just comparing pointers!


 void FindThingInArray (Thing* thing)
 {
 for (uint32 i = 0; i < vector.Count (); ++i)
 {
 if (vector == thing)
 return i;
 }
 }

This should work in all cases (where the pointers point to the same thing) right?
It seems too useful to be true.

My test program seems to work fine but is there some reason I shouldn't do this? (before i convert over loads of code)

jameszhao00

Oct 20, 2011 at 12:33 AM

Yes. C++ 's find

And also watch out. Using pointers as object identities may lead to issues down the road (serialization/deserialization, network, ...)

smasherprog

Oct 20, 2011 at 3:09 AM

also, check out your return type. Currently, it is void, but it should be something else.

latent

Oct 20, 2011 at 5:03 AM

but is there some reason I shouldn't do this?

Only if there's a chance you are comparying a *copy* of the object. ie...

[source lang="cpp"]
Thing b = *vector;
return FindThingInArray(&b); //fails in your second example, but succeeds in your first
[/source]

Vectorian

Oct 20, 2011 at 12:28 PM

Yes this always works. A 'common' issue with this beside the serialization etc. already mentioned is that you cannot replace instances if you use pointers as identifiers (ie. swap one object for another (most often of different derived types)).

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.