Whenever a table is passed through a BindableFunction or BindableEvent, it is copied before being sent on to the receiver, rather than being passed by reference. The relevant documentation doesn’t explain that this happens, which bugged me when I tried to use it with object-oriented programming.
More experienced developers can infer that this documentation’s stated restrictions means that JSON might be used, which in turn means tables are copied. Though newer developers who learned object-oriented programming before JSON will have a hard time without knowing these bindables duplicate tables.
Here’s a script that reproduces the table-duplication behavior.
-- Set up the system for testing.
OriginalTable = {Foo = "Hello."}
PassedTable = nil
ReturnedTable = nil
EventTable = nil
PassInTest = Instance.new("BindableFunction")
PassInTest.OnInvoke = function(t)
PassedTable = t
end
PassOutTest = Instance.new("BindableFunction")
PassOutTest.OnInvoke = function()
return OriginalTable
end
EventTest = Instance.new("BindableEvent")
EventTest.Event:Connect(function(t)
EventTable = t
end)
-- Begin testing.
print("--- Passing table to a BindableFunction. ---")
print("Original table -", OriginalTable)
PassInTest:Invoke(OriginalTable)
print("Function sees -", PassedTable)
print("Same? -", OriginalTable == PassedTable)
print("--- Getting table from another BindableFunction. ---")
print("Original table -", OriginalTable)
ReturnedTable = PassOutTest:Invoke()
print("Returned table -", ReturnedTable)
print("Same? -", OriginalTable == ReturnedTable)
print("--- Passing table through BindableEvent. ---")
print("Original table -", OriginalTable)
EventTest:Fire(OriginalTable)
print("Handler sees -", EventTable)
print("Same? -", OriginalTable == EventTable)
print("--- Editing Foo in table seen by BindableEvent. ---")
print("Original -", EventTable.Foo)
EventTable.Foo = "Good bye."
print("New -", EventTable.Foo)
print("Value in original table changed? -", OriginalTable.Foo == "Good bye.")
Output:
— Passing table to a BindableFunction. —
Original table - table: 0x7f472d427fddab75
Function sees - table: 0x88ebc8e8b93a3015
Same? - false
— Getting table from another BindableFunction. —
Original table - table: 0x7f472d427fddab75
Returned table - table: 0x9b0c7b4983c77b65
Same? - false
— Passing table through BindableEvent. —
Original table - table: 0x7f472d427fddab75
Handler sees - table: 0x69d7c09079fafca5
Same? - false
— Editing Foo in table seen by BindableEvent. —
Original - Hello.
New - Good bye.
Value in original table changed? - false
