So everything in ruby is an object, which means that when using format strings
with Objective-C methods like String+stringWithFormat and NSLog, the only
formatter that makes sense is "%@". Other formatters generally give unexpected
results. E.g. "%d" will print the value of the pointer to the number object.
(Or I think that's what it is.)
OTOH ruby itself is, by necessity, smarter in its own handling of format
strings. Kernel#sprintf and String#% will generally figure out a way to
shoehorn whatever object you're passing into the necessary format, e.g.:
"%d" % "4" # => "4"
"%d" % 4.1 # => "4"
Assorted observations:
- Newcomers will inevitably run into sad situations trying to use NSLog with %d
and getting really weird numbers.
- The inconsistency between the Objective-C and Ruby behaviors still feels
weird even though I understand why it is that way.
- As far as I know, there' no way to specify a non-object argument value (e.g.
int) in a ruby method call.
- I'm not sure there's a sane solution to this, e.g. if it's safe to translate
ruby objects into the necessary native C types on the fly.
- I wonder if, even after being painfully aware of this dichotomy, there will
still be pitfalls that can't be worked around:
- For example, how do I deal with localizedStringWithFormat? Ruby's native
methods aren't locale-aware.
- Or what about .strings localization files in a mixed Objective-C / MacRuby
app?
Has this been given any thought? What are the current plans / recommendations?
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