Possible bug with handling of default values for a method

ruby-talk
1

I have the following code snippet:

class SomeClass
def meth1( to = ‘default1’, msg = ‘default2’ )
…
end
end

param1 = nil ## value is nil because of selecting from a nullable db field
param2 = “Some Message”

sc.meth1( param1, param2 )

The to variable is nil inside meth1, it is not getting assigned the default
value. Is this is a bug in how ruby handles default values? Or is there
something I have wrong in my code? Any ideas?

2

If you pass nil into the first parameter, it will be nil. The defaults only get
used if you dont supply any argument.

sc.meth1(param1) # msg defaults to ‘default2’
sc.meth1 # to defaults to ‘default1’, msg defaults to ‘default2’

···

On Thu, Sep 19, 2002 at 07:15:51AM +0900, Berge, Robert wrote:

I have the following code snippet:

classSomeClass
def meth1( to = ‘default1’, msg = ‘default2’ )
…
end
end

param1 = nil ## value is nil because of selecting from a nullable db field
param2 = “Some Message”

sc.meth1(
param1, param2 )

–
Alan Chen
Digikata LLC
http://digikata.com

3

Ruby doesn’t fill in default values whenever you pass in nil; it fills
in default values whenever you don’t pass in a particular argument,
e.g.:

def foo(a=‘string1’, b=‘string2’)
p a
p b
end

foo(‘foo’, ‘bar’) #=> “foo”
“bar”
foo(‘foo’) #=> “foo”
“string2”
foo(‘foo’, nil) #=> “foo”
nil

If you want Ruby to fill in your default values whenever nil is passed
in, then you can write:

class SomeClass
def meth1(to=nil, msg=nil)
to ||= ‘default1’
msg ||= ‘default2’
p to
p msg
end
end

param1 = nil
param2 = “Some Message”

sc = SomeClass.new
sc.meth1( param1, param2 ) #=> “default1”
#=> “Some Message”

Hope this helps,

Paul

···

On Thu, Sep 19, 2002 at 07:15:51AM +0900, Berge, Robert wrote:

I have the following code snippet:

class SomeClass
def meth1( to = ‘default1’, msg = ‘default2’ )
…
end
end

param1 = nil ## value is nil because of selecting from a nullable db field
param2 = “Some Message”

sc.meth1( param1, param2 )

The to variable is nil inside meth1, it is not getting assigned the default
value. Is this is a bug in how ruby handles default values? Or is there
something I have wrong in my code? Any ideas?