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Recently some of our developers ran into the accusation that with a
dynamic language like ruby you use so many dynamic type checks that
you end up effectively writing your own type system. So they
thought, since we've written a lot of real ruby code - how often do
we make dynamic type checks? Michael Schubert gathered up the data. The table below contains the data. We define a dynamic type check
as the use of the methods is_a?, kind_of?,
and instance_of?. The lines of code come from the
standard rake stats command in rails.
| Project ID | Code | Test | LOC /
type check | test LOC /
code LOC |
|---|
type
checks | Lines
of Code | type
checks | Lines
of Code |
|---|
| A | 16 | 13318 | 0 | 9856 | 1448 | 0.7 | | B | 14 | 19138 | 0 | 17123 | 2590 | 0.9 | | C | 0 | 2607 | 0 | 2981 | ∞ | 1.1 | | D | 7 | 4265 | 3 | 4069 | 833 | 1.0 | | E | 32 | 29619 | 60 | 97688 | 1384 | 3.3 | | F | 18 | ~9500 | N/A | N/A | 528 | N/A | | G | 0 | 2455 | 0 | 3290 | ∞ | 1.3 | | H | 9 | 2220 | 6 | 6404 | 575 | 2.9 | | I | 23 | 10633 | 2 | 12331 | 919 | 1.2 | | J | 196 | 40461 | 24 | 88511 | 586 | 2.2 | | K | 17 | 5769 | 6 | 9848 | 679 | 1.7 |
The moral of this data is that you shouldn't expect to see a lot of
type check calls in your ruby code base. This, of course, is true of
any dynamic language. It was generally considered bad form in
Smalltalk circles I inhabited too. The methods that were checked for in this data aren't the only ones
that can be considered a dynamic type check. Other cases are
respond_to? and aClass === anInstance. Our
folks felt that these cases were no more common than the ones they
checked for. Most uses are those of dealing with liberal input - eg where a method
parameter can be a string, symbol, or array. These crop up in DSLish
situations where you want liberal input for the high readability.
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