# Check

This function checks the given arguments and calls the error-function if something is wrong. Finally it makes debugging easier since you'll get useful error-messages when calling a selfmade function with wrong or malformed arguments.

## Syntax

    void Check( string funcname, var types1, var arg1, string argname1, [ ... ] )

### Required Arguments

- funcname: Name of the function in which the Check-function is called.
- types1: Type(s) that arg1 should/may be of. It's a string if only one type is possible, otherwise it can be a table with strings. Possible types are "nil", "boolean", "number", "string", "function", "table", "thread" and "userdata".
- arg1: Value of the argument that should be checked.
- argname1: Name of the argument whose value is arg1.

### Optional Arguments

- ...: You may pass as many triples as you want to.

## Source

    function Check(funcname, ...)
        local arg = {...}

        if (type(funcname) ~= "string") then
            error("Argument type mismatch at 'Check' ('funcname'). Expected 'string', got '"..type(funcname).."'.", 2)
        end
        if (#arg % 3 > 0) then
            error("Argument number mismatch at 'Check'. Expected #arg % 3 to be 0, but it is "..(#arg % 3)..".", 2)
        end

        for i=1, #arg-2, 3 do
            if (type(arg[i]) ~= "string" and type(arg[i]) ~= "table") then
                error("Argument type mismatch at 'Check' (arg #"..i.."). Expected 'string' or 'table', got '"..type(arg[i]).."'.", 2)
            elseif (type(arg[i+2]) ~= "string") then
                error("Argument type mismatch at 'Check' (arg #"..(i+2).."). Expected 'string', got '"..type(arg[i+2]).."'.", 2)
            end

            if (type(arg[i]) == "table") then
                local aType = type(arg[i+1])
                for _, pType in next, arg[i] do
                    if (aType == pType) then
                        aType = nil
                        break
                    end
                end
                if (aType) then
                    error("Argument type mismatch at '"..funcname.."' ('"..arg[i+2].."'). Expected '"..table.concat(arg[i], "' or '").."', got '"..aType.."'.", 3)
                end
            elseif (type(arg[i+1]) ~= arg[i]) then
                error("Argument type mismatch at '"..funcname.."' ('"..arg[i+2].."'). Expected '"..arg[i].."', got '"..type(arg[i+1]).."'.", 3)
            end
        end
    end

## Example

This example shows the Check-function's usage in case of a more or less useless division function.

    function divide(dividend, divisor, round)
        -- check the passed arguments
        Check("divide", "number", dividend, "dividend", "number", divisor, "divisor", {"nil","boolean"}, round, "round")

        -- error if divisor is 0
        if (divisor == 0) then error("Someone tried to divide by 0. YOU MUST NOT DO THAT!!!") end

        -- calculate the result
        local quotient = dividend / divisor
        -- round the result if round is true
        if (round) then quotient = math.floor(quotient + .5)

        -- return the result
        return quotient
    end

Category:

- Snippets