Array.rand fails - Why?

Rails
1

Hey guys.

I have bould an array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] and want to get a
random element from it. If i use array.rand the controller returns this
error

private method `rand' called for [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]:Array

Why is the rand private, and cannot be accesed naturally on all and/or
any array element?

2

On 4 Mar 2008, at 09:15, Emil K. wrote:

private method `rand’ called for [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]:Array
[/code]

Why is the rand private, and cannot be accesed naturally on all and/or
any array element?

It’s private in a ‘normal’ array. My guess is that it’s because that
rand method isn’t the rand method you think it is (ie it doesn’t
return a random element from it), so making it public would invite
confusion. The version of activesupport in rails 2 adds a public rand
method that does do what you want. It’s nothing fancy though, just
some_array[Kernel.rand(some_array.length)]

Fred

3

Emil K. wrote:

I have bould an array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] and want to get a
random element from it. If i use array.rand the controller returns this
error

private method `rand' called for [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]:Array

Why is the rand private, and cannot be accesed naturally on all and/or
any array element?

#rand is actually defined as a global function. It doesn’t take a
receiver in the core code.

To get a random element of an array:

a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a[rand(a.length)]

If you want to apply it as a method, you can define something like:

class Array
def rand
self[super(self.length)]
end
end

or:
class Integer
def rand
super self
end
end
class Array
def rand
self[self.length.rand]
end
end

4

Mark B. wrote:

To get a random element of an array:

a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a[rand(a.length)]

If you want to apply it as a method, you can define something like:

class Array
def rand
self[super(self.length)]
end
end

or:
class Integer
def rand
super self
end
end
class Array
def rand
self[self.length.rand]
end
end

Thank you for the help! =) I got the hang of it now I should think.

  • Emil