# Adding \*each\*

**URL:** <https://www.ruby-forum.com/t/adding-each/193676>\
**Category:** Ruby\
**Created:** [August 21, 2010, 7:46pm UTC](https://www.ruby-forum.com/t/adding-each/193676 "2010-08-21T19:46:28Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\
**Post date:** [August 21, 2010, 7:46pm UTC](https://www.ruby-forum.com/t/adding-each/193676/1 "2010-08-21T19:46:28Z")

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I’m trying to wrap my head around how to do an “each” for objects of a  
class that I have created.

Consider this contrived example  
class X  
def initialize  
@x = [10, ‘a’, ‘c’, 9, 8]  
end  
end

In Ruby 1.8, what’s the magic incantation so that I can do

x = X.new  
x.each {|y| puts y}

I have read and reread Dave T.'_Programming Ruby 1.9_ and … well  
… I think I have to define _each_ in class X and add some enumerable  
stuff … but … I just don’t get it.

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**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\
**Post date:** [August 21, 2010, 8:35pm UTC](https://www.ruby-forum.com/t/adding-each/193676/2 "2010-08-21T20:35:39Z")

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On Sun, Aug 22, 2010 at 2:45 AM, Ralph S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> Â x = X.new  
> Â x.each {|y| puts y}
> 
> I have read and reread Dave T.'_Programming Ruby 1.9_ and … well … Â I think I have to define _each_ in class X and add some enumerable stuff … but … I just don’t get it.

class X  
include Enumerable

def initialize  
@x = [10, ‘a’, ‘c’, 9, 8]  
end

def each(&block)  
@x.each(&block)  
end  
end

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<div class="post-metadata">

**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\
**Post date:** [August 22, 2010, 11:21am UTC](https://www.ruby-forum.com/t/adding-each/193676/3 "2010-08-22T11:21:39Z")

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On Saturday, August 21, 2010 12:45:49 pm Ralph S. wrote:

> In Ruby 1.8, what’s the magic incantation so that I can do
> 
> x = X.new  
> x.each {|y| puts y}

You can do that anyway, it just doesn’t do anything. All methods can  
accept a  
block, whether you want them to or not. All you have to do is yield to  
it.

> I have read and reread Dave T.'_Programming Ruby 1.9_ and … well …  
> I think I have to define _each_ in class X and add some enumerable stuff

First, why are you reading a 1.9 book and applying it to 1.8?  
Not that it should matter…

You have to define ‘each’, yes, and you probably should include  
enumerable.  
I’ll give a contrived solution to your contrived example:

class X  
def each  
yield @x[0]  
yield @x[1]  
…  
end  
end

That ‘yield’ is a call to whatever block you passed. You could, of  
course,  
wrap it in a loop, or even an enumerator of its own:

class X  
def each  
@x.each {|x| yield x}  
end  
end

In this specific case, your contrived example is just contrived enough  
that we  
could take it a step further. You can grab that block as an actual  
argument by  
prefixing it with &, and apply it the same way. So, you can just pass it  
straight through, as Michael F. suggested:

class X  
def each(&block)  
@x.each(&block)  
end  
end

It’s contrived, but we may as well finish it up:

class X

# adds map, select, and so on

include Enumerable

def each(&block)  
# enum\_for makes a new enum which uses ‘each’ by default  
return enum\_for if block\_given?  
@x.each(&block)  
end  
end

I don’t always include Enumerable, but I do always do enum\_for, because  
not  
everything I want to enumerate is already in a form I can call ‘each’  
on. For  
example:

class Foo  
def all\_bars  
return enum\_for :all\_bars unless block\_given?  
yield :bar  
yield :foobar  
yield :baz  
end  
end

Now I can do crazy stuff like:

Foo.new.all\_bars.map(&:to\_s)  
Foo.new.all\_bars{|b| puts b}

That way, I can have multiple methods like that, each of which either  
behaves  
as the appropriate iterator, or gives me an appropriate enumerable (an  
enumerator, specifically) to play with.

> I just don’t get it.

I hope I’ve helped, but if not, I’m going to need more than that. If you  
still  
don’t get it, let me know what you don’t get, and we can go from there.