How to pass a variable to a method in an existing class?

Ruby
1

Hi,

I am a new ruby user and I want to add a function to an existing class.
I googled the answer and found part of the solution. All findings on the
web adding a new method without a variable. In my case I want to use the
string as a variable. Here is what I want to do:
class String

def convert(x)
#code to convert the x
x.upcase
end
end

What I want is in the irb I can use the new method in the way as:

“a”.convert

This will convert a to upper case. However, it does not take the “a” as
the input variable and generating error
ArgumentError: wrong number of arguments (0 for 1)

How do I acheive what I want?

Thanks

Frank

2

“self” is a pointer to an actual element. So if you write:
class String
def convert
self.upcase
end
end

It’ll be perfectly fine.

Yours
Martin

2011/9/1 yw hi [email protected]:

3

–Marcin’s way is perfect; but there is something we don’t understand
about your requirement:

"…I want to use the string as a variable

def convert(x)

#code to convert the x
…"

then…"in the irb I can use the new method in the way as:

“a”.convert <—what’s happened to ur variable x???

Best Regards,

frank hi wrote in post #1019491:

Hi,

I am a new ruby user and I want to add a function to an existing class.
I googled the answer and found part of the solution. All findings on the
web adding a new method without a variable. In my case I want to use the
string as a variable. Here is what I want to do:
class String

def convert(x)
#code to convert the x
x.upcase
end
end

What I want is in the irb I can use the new method in the way as:

“a”.convert

This will convert a to upper case. However, it does not take the “a” as
the input variable and generating error
ArgumentError: wrong number of arguments (0 for 1)

How do I acheive what I want?

Thanks

Frank

4

Martin’s answer solved my problem.

Basically, I wrote my own method and want to add to the existing class
and expected that the “string”.convert will pass the “string” to the
method. However, I could not find the solution to let the convert method
takes the “string” as input. the self pointer solved the issue.

Thanks

Frank