Is it Necessary to add a check for nil? Here is an example:
pie=workspace.Pie
if pie ==nil then
print("xP Pi")
end
Do you **Have **to add it or do you add it whenever you want to?
Please Respect that I am a Beginner in need of knowledge
✓ ANSWER ACCEPTED
Why do You have to check for nils?
2 answers
✓ Accepted answer
It depends on the situation. Typically, it isn't necessary; to quote the Lua reference manual (2.4.4):
Both false and nil are considered false. All values different from nil and false are considered true (in particular, the number 0 and the empty string are also true).
This means that if false then is equivalent to if nil then and if workspace:FindFirstChild("Pie") then is equivalent to if true then (assuming workspace.Pie exists; if you're not sure if it exists, you should use workspace:FindFirstChild("Pie") instead of workspace.Pie so that it returns nil in case it doesn't exist, instead of erroring).
As such, the following two pieces of code are equivalent, too:
pie = workspace:FindFirstChild("Pie")
if pie == nil then
...
end
pie = workspace:FindFirstChild("Pie")
if not pie then
...
end
Using not pie would technically being equivalent to using the expression pie == nil or pie == false, which comes down to the same thing as pie == nil if FindFirstChild is used to get the value.
Imagine you want a function that prints the argument unless no argument was given. You could do this:
function foo(arg)
if arg ~= nil then
print(arg)
end
end
Converting the ~= nil check would turn it into this:
function bar(arg)
if arg then
print(arg)
end
end
If you were to use foo("banana") and bar("banana"), they would both print "banana". If you used foo() and bar(), neither of them would print anything, as expected.
However, if you were to use foo(false) and bar(false), then foo would print "false", while bar would print nothing.
Aside from this subtle difference, they come down to the same thing though.
First off, if the object was nil,
pie=workspace.Pie
^That would give you an error.
One way to obtain the condition of nil is by using the method FindFirstChild.
What FindFirstChild does is it returns the object that appears with the given name. If there is no object with that name, it returns nil.
So rather you can do:
pie=workspace:FindFirstChild("Pie")
if pie ==nil then
print("xP Pi")
end
1 comment
0
Its really a Double check?
This discussion is preserved as it was. New answers, comments, and votes are closed.
4 comments
So checking with the nils and falses, is just double checking your script?
@TheContinentofEurope I'm not sure what you mean; are you talking about using
if x thenas opposed toif x ~= nil and x ~= false then? I meant that those are equivalent, but you should be careful of what the implications are in cases where it actually matters whetherxisnilorfalse, unlike in cases such as checking the result of FindFirstChild which will only return nil or an instancePlease don't thumbs down me.
@TheContinentofEurope I have never thumbed down anyone on this site so far. Please don't jump to conclusions like that.