The second argument

ruby-talk
1

Hello,

what's the argument of "obj" in: def []=(index,obj) ?

I don't see it call this method with the second argument.
Thanks

The original code is:

class Array2 < Array

  def [](index)
    if index>0
      super(index-1)
    else
      raise IndexError
    end
  end

  def []=(index,obj)
    if index>0
      super(index-1,obj)
    else
      raise IndexError
    end
  end

end

x = Array2.new

x[1]=5
x[2]=3
x[0]=1 # Error
x[-1]=1 # Error

2

Hello,

what's the argument of "obj" in: def =(index,obj) ?

I don't see it call this method with the second argument.
Thanks

The original code is:

class Array2 < Array

def (index)
if index>0
super(index-1)
else
raise IndexError
end
end

def =(index,obj)
if index>0
super(index-1,obj)
else
raise IndexError
end
end

end

x = Array2.new

x[1]=5

This is syntactic sugar for

x.=(1,5)

which is the method you are asking about.

x[2]=3
x[0]=1 # Error
x[-1]=1 # Error

Jesus.

···

On Fri, Nov 5, 2010 at 9:10 AM, wroxdb <wroxdb@gmail.com> wrote:

3

It's the value on the right of the equals sign:

a[index] = obj

is the same as

a.=(index, obj)

As Jesús pointed out, Ruby supplies syntactic sugar to allow methods
to be called using the syntax of an operator. For example:

5 + 5

is really calling the method "+" on an instance of Fixnum and passing
it the value 5 as an argument:

5.+(5)

Try it in irb:

irb(main):001:0> 5.+(5)
=> 10
irb(main):002:0>

Because operators are really methods, you can define them on your own
classes or override them if needed.

···

On Fri, 5 Nov 2010 03:10:26 -0500, wroxdb <wroxdb@gmail.com> wrote in <AANLkTi=yqFwJvMBi=yZdLj2Rr8rbTQ3pT6tRP8tkCQn1@mail.gmail.com>:

what's the argument of "obj" in: def =(index,obj) ?

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Charles Calvert | Software Design/Development
Celtic Wolf, Inc. | Project Management
http://www.celticwolf.com/ | Technical Writing
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