CODEWITHSUNDEEP
lua
Martin Ma
Martin Ma

Reputation: 150

How to check if value is string in lua?

Hello guys i please need your help. I have values, most of them are numbers but some of them are strings. How can i check if value is string or number?

I already tried this code but when it reach string value i get error " attempt to perform arithmetic on local 'numberValue' (a nil value)"

function Config:IsNumber(value)
    if value ~=nill or value ~=nil then                 
        local numberValue = tonumber(value)
        if numberValue/numberValue ==1 then
            return true
        else
            return false
        end
    end
end
end
end

Upvotes: 0

Views: 10035

Answers (1)

Piglet
Piglet

Reputation: 28950

First of all let's start with errors in your code.

  • You have 2 ends to many.
  • it is nil, not nill. I'm not sure where you're going with that check.

Other issues / things to improve:

numberValue / numberValue == 1 does not make any sense. A number divided by itself always results in 1. So checking that is pointless.

Also instead of

if something == 1 then
  return true
else
  return false
end

Can simply be replaced by return something == 1. There is no need for a conditional statement here.

To your question:

To check wether a value is a string use type(value) == "string".

To check wether a value can be converted to a number use tonumber(value). It will either return a number or nil.

So according to your error the conversion to a number failed.

If you don't know for sure that your value can be converted to a number, you should ensure that tonumber succeeded before you do any operations on its return value.

local numberValue = tonumber(value)
if not numberValue then
  print("converting value to a number failed")
  return
end
-- at this point you know numberValue is a number

So if you wanted to write a function that ensures a string represents a number you could do something like this:

function IsNumber(value)
  return tonumber(value) and true or false
end

Upvotes: 3

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