I made this for checking types during runtime. It’s designed specifically for Roblox, but also works in Lua5.1.
Give it a try, let me know if you have any questions or if the documentation could be more clear anywhere.
61 Likes
Added error messages as a second return value from type checkers.
If you wrap your type check in an assert you’ll get the error message on failure:
assert(t.number("1")) --> number expected, got string
(these can get pretty complex based on your type definitions)
Different example:
local success, errMsg = t.number("1")
if success then
-- do stuff
else
warn(errMsg)
end
4 Likes
this is something ive always wanted to have but ive always been too lazy to make
very good 10/10
3 Likes
How would you check that a number isn’t nan, +inf, or -inf?
(No reason, really. Just thought that someone may need to know this if the domain of a function is all real numbers. I’m using this library for my game <3)
1 Like
There isn’t a check built in for this, but you could totally make your own. (See tips and tricks in the readme)
I’ll consider adding something like this in the future.
1 Like
This… is just wonderful.
1 Like
Thanks, let me know if anything was confusing with the documentation.
Did you find any cool (or not obvious) uses for it?
Not any particularly non-obvious uses, the documentation is good.
Interestingly enough I made a runtime type checker a while ago.
The main difference is that I wanted to bind signatures to functions themselves, here’s an example.
local myFunction = validate("number", "string", function (a, b)
print("Valid")
end)
myFunction(1, "Hi")
-- Valid
myFunction("Test")
-- Error: bad argument #1 to 'myFunction' (number expected, got string)
I realized that overrides were also quite important so added in support for them too.
myFunction:AddSignature("string")
myFunction("Test")
-- Valid
There is also support for varargs, so you can specify the type as ... and it’ll match any type.
local myOtherFunction = validate("function", "...", function (f, ...)
f(...)
end)
3 Likes
If there’s one thing I dislike about this library, it’s the name. Too short and makes it hard to search for (via Google, DevForum search)
1 Like
That’s definitely a downside to the name, but many people dislike having a different variable name from the library name. So a single letter encourages a short variable name. More complex type definitions require you to repeat the variable name often in the same line.
1 Like
Just wanted to dump a bunch of checker I found a use for in my game:
do
local function isNan(n)
return n ~= n
end
function t.nan(value)
local success, errMsg = t.number(value)
if not success then
return false, errMsg or ""
end
if isNan(value) then
return true
else
return false, string.format("NaN expected")
end
end
function t.notNan(value)
local success, errMsg = t.number(value)
if not success then
return false, errMsg or ""
end
if not isNan(value) then
return true
else
return false, string.format("non-NaN expected")
end
end
end
do
local function isFinite(n)
return n > -math.huge and n < math.huge
end
function t.finite(value)
local success, errMsg = t.number(value)
if not success then
return false, errMsg or ""
end
if isFinite(value) then
return true
else
return false, string.format("finite expected")
end
end
function t.infinite(value)
local success, errMsg = t.number(value)
if not success then
return false, errMsg or ""
end
if not isFinite(value) then
return true
else
return false, string.format("infinite expected")
end
end
end
function t.real(value)
local success, errMsg = t.notNan(value)
if not success then
return false, errMsg or ""
end
local success, errMsg = t.finite(value)
if not success then
return false, errMsg or ""
end
return true
end
function t.realVector3(vector)
local success, errMsg = t.Vector3(vector)
if not success then
return false, errMsg or ""
end
local success, errMsg = t.real(vector.magnitude)
if not success then
return false, "vector components are not all real"
end
return true
end
function t.unitVector3(vector)
local success, errMsg = t.Vector3(vector)
if not success then
return false, errMsg or ""
end
if vector.magnitude == 1 then
return true
else
return false, "unit vector expected"
end
end
t.alpha = t.numberConstrained(0, 1)
function t.integerMin(min)
assert(t.integer(min))
return function(value)
local success, errMsg = t.integer(value)
if not success then
return false, errMsg or ""
end
if value >= min then
return true
else
return false, string.format("integer >= %d expected", min)
end
end
end
function t.integerMax(max)
assert(t.integer(max))
return function(value)
local success, errMsg = t.integer(value)
if not success then
return false, errMsg or ""
end
if value <= max then
return true
else
return false, string.format("integer <= %d expected", max)
end
end
end
function t.integerConstrained(min, max)
assert(t.integer(min) and t.integer(max))
local minCheck = t.numberMin(min)
local maxCheck = t.numberMax(max)
return function(value)
local integerSuccess, integerErrMsg = t.integer(value)
if not integerSuccess then
return false, integerErrMsg or ""
end
local minSuccess, minErrMsg = minCheck(value)
if not minSuccess then
return false, minErrMsg or ""
end
local maxSuccess, maxErrMsg = maxCheck(value)
if not maxSuccess then
return false, maxErrMsg or ""
end
return true
end
end
t.nonNegativeInteger = t.integerMin(0)
function t.equals(valueToEquals)
return function(value)
if value == valueToEquals then
return true
end
return false, "two values are not equal."
end
end
function t.notEquals(valueToNotEquals)
return function(value)
if value ~= valueToNotEquals then
return true
end
return false, "two values are not unequal."
end
end
PS: I’m using this library to make sure that clients are not sending bad data to my remotes. Can you think of any reason why I shouldn’t be doing this with your library?
1 Like
That is a perfectly valid use case! It’s why I originally wrote the library.
And thanks for posting this, these are great examples of custom type checkers.
1 Like
May need to be a little careful with your unitVector3 - the magnitude of a vector produced by .unit or documented as unitary in the API references is not guaranteed to always equal exactly 1 as far as I’m aware. It may instead be off by a very small amount - you could use an epsilon to catch these.
4 Likes
Do you think vector == vector.unit is a good way of checking whether or a vector is a unitvector? Would be odd if the value of vector.unit changed every time I got it.
I’m not sure. I’d suggest instead that you just do something like
local abs = math.abs
local eps = 0.0001
-- stuff
return abs(vec.magnitude - 1) < eps
1 Like
I suppose. I was hoping to avoid using arbitrary eps but then again it’s not like any of my use cases require such precision.
I was able to reproduce this, which makes sense. Not something I’ve thought about.
local vec = Vector3.new(0.0001, 0.0001, 0.0001).Unit
print(vec.Magnitude) -- 0.99999994039536
1 Like
Wow this is just silly.
local vec = Vector3.new(0.0001, 0.0001, 0.0001).Unit
print(vec.magnitude)
vec = vec.Unit
print(vec.magnitude)
prints
0.99999994039536
1.0000001192093
Doing it again flip-flops between the two values.
1 Like
Two new functions were added:
t.exactly can be used to compare a value to another by ==. Pair this with t.union to create a list of options for a type.
t.strictInterface which allows interface checking that errors with extra fields.
You can find out more about both of these in the project readme.
3 Likes