[Zefk]

How does a pcall or xpcall error message work with a metatable?
http://www.solarus-games.org/doc/latest/lua_api_main.html#lua_api_main_get_metatable

[Christopho]

What do you mean?

[Zefk]

If the function fails, then I'd like to give a custom message.

Code: ( lua) [Select]

function myfunction()
   n = n/nil
end

if pcall(myfunction) then
   print("Success")
else
   print("Failure")
end

[Christopho]

Your code is a correct way to catch errors.
But you were talking about metatables in your first message, what do you want to know exactly?

I don't know if it answers your question, but sol.main.get_metatable() returns nil if the parameter is an unknown type name. It will only throw an error if the parameter is missing or is not a string.

[Zefk]

Is it possible to pcall something like the following?

example.lua

Code: ( lua) [Select]


local metatable = sol.main.get_metatable("custom_entity")

function metatable:example()
  --some code
end

main.lua

Code: ( lua) [Select]

require(scripts/example.lua)
custon entity:

Code: ( lua) [Select]

entity:example()

if pcall (example) then

  print("success")

else
 
   print("fali")

end

[Diarandor]

Note that your "example" variable, inside pcall, is nil. And that space between pcall and the parenthesis may give an error, but I am not sure.

[Christopho]

Ok, so your question is actually independent from metatables or Solarus, it is about the passing a value of type function vs calling a function.

Code: ( lua) [Select]

function metatable:example()
  --some code
end
This defines a field "example" (of type function) on the object "metatable", and not an "example" global value.

Which means that you can call it like this, assuming you  have an entity called my_entity:

Code: ( lua) [Select]

my_entity:example()and not like this

Code: (lua) [Select]

example() -- Does not work: example is nil
If you want to make a value of type function instead of doing the call entity:example(), just wrap the call it in a function:

Code: (lua) [Select]

local function f()
  my_entity:example()
endThen it is a value of type function (and not a function call anymore, this is the trick!) so you can pass it to anything that wants a value of type function, like pcall, sol.timer.start, etc.

Code: (lua) [Select]

local success = pcall(f)
if success then
  ...
else
  ...
end

You can even keep it anonymous if you prefer:

Code: (lua) [Select]

local success = pcall(function()
  entity:example()
end)
if success then
  ...
else
  ...
end


[Zefk]

@Christopho
That was a perfect explanation. Thank you Christopho!