Attempt to call method (a nil value)

[virus7072]

Hey all,

Quick question. I like to think of myself as a pretty good coder, however, I always run across 'Attempt to call method (a nil value)' errors and have issues trouble shooting them. I always end up troubleshooting the code and fixing the issue. However, I have yet to find a pattern with these errors.

Is there any kind of rule of thumb on what causes these errors? If so, I'm sure it would help me tremendously with troubleshooting.

Thanks!

[Brandan]

As far as I know, nil means it doesn't exist. Like, when a player spawns, you might set
ply.DidHeSpawn=true

and later, maybe when he dies, you print ply.DidHeSpawn, if it's nil, then the code to set ply.DidHeSpawn=true didn't get executed. Which means ply.DidHeSpawn is nil.

[Wunce]

[url]http://wiki.garrysmod.com/?title=Gmod_Lua_Error_List[/url]

also to avoid getting nil values use

[lua]
if ply.avalue then
-- means it isn't nil/false
else
-- means it is nil or false
end
[/lua]

[_nonSENSE]

[QUOTE=virus7072;28203044]Hey all,

Quick question. I like to think of myself as a pretty good coder, however, I always run across 'Attempt to call method (a nil value)' errors and have issues trouble shooting them. I always end up troubleshooting the code and fixing the issue. However, I have yet to find a pattern with these errors.

Is there any kind of rule of thumb on what causes these errors? If so, I'm sure it would help me tremendously with troubleshooting.

Thanks![/QUOTE]

You usually get the 'Attempt to call method (a nil value)'-error when you are trying to use a function in a library that does not exist in the environment it was executed (client/server). Example: Using the vgui, surface, draw libraries on the server.

[virus7072]

[QUOTE=Brandan;28203136]As far as I know, nil means it doesn't exist. Like, when a player spawns, you might set
ply.DidHeSpawn=true

and later, maybe when he dies, you print ply.DidHeSpawn, if it's nil, then the code to set ply.DidHeSpawn=true didn't get executed. Which means ply.DidHeSpawn is nil.[/QUOTE]

Right, I was under the same impression, I just didn't know how it applied when calling functions.

[QUOTE=Wunce;28203947][url]http://wiki.garrysmod.com/?title=Gmod_Lua_Error_List[/url]

also to avoid getting nil values use

[lua]
if ply.avalue then
-- means it isn't nil/false
else
-- means it is nil or false
end
[/lua][/QUOTE]

Thank you, I was looking for a wiki link, I couldn't find one. Also, thanks for the tip.

[QUOTE=_nonSENSE;28207490]You usually get the 'Attempt to call method (a nil value)'-error when you are trying to use a function in a library that does not exist in the environment it was executed (client/server). Example: Using the vgui, surface, draw libraries on the server.[/QUOTE]

Thanks for that, I noticed I had a syntax error in the one I was editing, I'm just used to it spitting up the exact error and not an error calling the function.

Thanks all for the help!