Is there any way to protect an instance variable from being written to/modified in Ruby?
Say I do this:
class Test
def initialize(var)
@var = var
end
def modify
@var = "test" # This would raise an error, saying '@var' is just readable.
end
end
Is there any way to make instance variable to be read-only? If not, which kind of attribute am I looking for?
You can virtually protect instance variables with freezing a wrapping object:
t=Test.new "example"
p t.var
# "example"
t.freeze
t.modify
# :in `modify': can't modify frozen Test (RuntimeError)
p t.var
# t.var is still equal to "example" if exception won't terminate app
See Object#freeze method for details.
Test. You cannot add, delete, modify pointers but you can modify in place - data that those pointers refer too(C terms). In order to really protect you must freeze variable itself. Check this: gist.github.com/nedzadarek/7536766There is no way to do that. First of all, there should not be a reason that a class would need to write-protect an attribute against itself. Secondly, all access protection rules in Ruby, such as it exists, are really only suggestions - ultimately, using introspection, you can access anything you wish, including redefining core methods like Fixnum#+. Try this:
class Fixnum
def +(other)
self - other
end
end
It will mess up your code more than writing to @var ever could.
def 2.ff; endNo, there is no way to do this. The closest thing Ruby has to non-writable variables are constants which can exist within a class or module and begin with a capital letter (typically all caps). Ruby will not prevent these variables from being written, but will issue a warning if they are redefined.
