Loops in Ruby

[webbieguy]

Hi,

I have a very simple problem. I am a newbie to rails and for the life
of me can't figure out why a simple incrementing loop is not printing
to screen correctly. I know this has to be something simple but can't
find anything specific to my problem.

<%=
for i in 0..10 do
puts "i is now #{i}"
end
%>

Prints to screen "0..10" as opposed to what I want:

0
1
2
3
4
5
6
7
8
9
10

Can someone help me with this very simple problem. I have tried
until, .times, and while loops to no avail. So there must be some type
of syntax magic I am missing.

Thanks in advance,
Justin

[Frederick Cheung]

On Dec 30, 6:39 pm, webbieguy <justin.dean.griff...@gmail.com> wrote:
> Hi,
>
> I have a very simple problem. I am a newbie to rails and for the life
> of me can't figure out why a simple incrementing loop is not printing
> to screen correctly. I know this has to be something simple but can't
> find anything specific to my problem.
>
> <%=
> for i in 0..10 do
> puts "i is now #{i}"
> end
> %>
>

Because in a view you don't use puts (puts either goes nowhere or to a
logfile somewhere).
The <%= stuff the result of the chunk of code into the view, for a
'for' statement like you've got there then the result is the thing
iterated over (ie 0..10).

you want something more like

<% looping construct of your choice do %>
i is now <%= i %>
<% end %>

Fred

[Rob Biedenharn]

On Dec 30, 2009, at 4:08 PM, Frederick Cheung wrote:
> On Dec 30, 6:39 pm, webbieguy <justin.dean.griff...@gmail.com> wrote:
>> Hi,
>>
>> I have a very simple problem. I am a newbie to rails and for the life
>> of me can't figure out why a simple incrementing loop is not printing
>> to screen correctly. I know this has to be something simple but can't
>> find anything specific to my problem.
>>
>> <%=
>> for i in 0..10 do
>> puts "i is now #{i}"
>> end
>> %>
>>
> Because in a view you don't use puts (puts either goes nowhere or to a
> logfile somewhere).
> The <%= stuff the result of the chunk of code into the view, for a
> 'for' statement like you've got there then the result is the thing
> iterated over (ie 0..10).
>
> you want something more like
>
> <% looping construct of your choice do %>
> i is now <%= i %>
> <% end %>
>
> Fred

In addition to what Fred says, your other problem is that you have:
for i in <Range> do
#stuff
end
and you want: (note there's no 'do' on a for loop)
for i in <Range>
#stuff
end
so that would be:
for i in 0..10
#stuff
end

You're getting "0..10" because that's the value of the expression in
the <%= %>
Try this in irb and you'll see.
irb> for i in 0..10
irb> puts i
irb> end

0
1
2
3
4
5
6
7
8
9
10

=> 0..10
irb>

It's more likely, you want to have:

<% (0..10).each do |i| %>

i is now <%= i %>
<% end %>

The difference being mainly that the local variable i will only exist
inside the block and iterating over a collection using .each is much
more common. See James Gray's article "Shades of Gray: The Evils of
the For Loop" for a more thorough explanation.

http://blog.grayproductions.net/articles/the_evils_of_the_for_loop

-Rob

>> Prints to screen "0..10" as opposed to what I want:
>>
>> 0
>> 1
>> 2
>> 3
>> 4
>> 5
>> 6
>> 7
>> 8
>> 9
>> 10
>>
>> Can someone help me with this very simple problem. I have tried
>> until, .times, and while loops to no avail. So there must be some
>> type
>> of syntax magic I am missing.
>>
>> Thanks in advance,
>> Justin
>

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>

Rob Biedenharn http://agileconsultingllc.com
R...@AgileConsultingLLC.com

[David]

<% 0.upto(10) do |i| %>

i is now <%= i %>
<% end %>

[webbieguy]

Thank you! I figured it was just a simple thing I was doing wrong.
Much appreciation!!

Justin

[Conrad Taylor]

Actually, in the above, the 'do' is optional for both 'while', 'until, and 'for' loops

in both Ruby 1.8.x and 1.9.x.  Thus, the above is legal Ruby.  Furthermore, 

one can write the above using a colon as follows in Ruby 1.8.x:

for i in <Range> :

  #stuff

end

-Conrad

 

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