well, depends on semantics I guess
The discrete 'lines' that you see with the iron filings are not real... Imagine a contour map of a mountain- the elevation change does not happen in discrete jumps... The magnetic field is just that- a field....
Lets take an example- a charged particle shot into a magnetic field- it does not interact with a 'line of force' then travels a bit and hit another one-- it interacts in a continuous way with the field...
(By the way, the addition of the filings modifies the field of that bar magnet... the filings themselves become bar magnets and self order themselves along contours the field- they form a contour map of the field)