A bizarre problem with data= methods

Ruby
1

Hi all.

I have found an error that does not understand. Look this simple code:

class Foo
def value=(data)
puts “Look #{data}”
end
end

f = Foo.new.value = “at me” # => Look at me

Great! A little assigner that works perfectly. But now I make a
constructor that use the assigner directly:

class Foo
def initialize(data)
value = data
end

def value=(data)
puts “Look #{data}”
end
end

f = Foo.new(“at me”) # => Nothing!!!

Why? The constructor doesn’t use value= method. What is happening? Is
that normal?

Thanl you for your help.

2

2009/8/27 David E. [email protected]

end
that normal?
You need an explicit self, ie. self.value = data. Without the self,
Ruby
interprets that line as a local variable assignment, not a method call.

3

On Thursday 27 August 2009, David E. wrote:

|
| end
|that normal?
|
|Thanl you for your help.
|

Because when ruby sees something like:

identifier = value

it thinks you’re creating a local variable called identifier, not
calling the
identifier= method. To force ruby to understand you want to call the
method,
you need to use the dot notation, self.identifier = value, or use send:
send(:identifier=, value).

I hope this helps

Stefano

4

El jueves 27 de agosto, James C. escribió:

You need an explicit self, ie. self.value = data. Without the
self, Ruby interprets that line as a local variable assignment, not
a method call.

It has sense. Other form, Ruby might search all methods of class in each
local assignment.

Thank you.