How do I define a for-loop in Ruby?

I have been looking at the ruby-docs but h开发者_运维百科ave not been able to make sense of them. I have an application that generates a table and stores files in each cell, a user can add another file by clicking on the last box which says "Add file", but I can't figure out how to do this in ruby.

In PHP I would do something like this; if it helps anyone get an idea:

for($i = 0; $i <= $file_array.size; $i++){
  if($i%3=0){
   html .= "</tr><tr>"
  }
  if($i == $array.size){
   //Prevents out of bounds error
   html .= "<td><a href=\"...\">New File Link</a></td>"
  }
 else{
  //We are not out-of-bounds; continue.
  html .= "<td><a href=\"$file_array[$i]\">File Link</a></td>"
 }
}

In ruby I have

 object.files.each_with_index |attachment, i|

but, I don't know if that is what I want to use; I can't figure out how to use it.

Update: I forgot to put table cells in the code.

Ruby's each and each_with_index are kind of like PHP's foreach loop. The variable attachment will be the element of the array:

html = ""
object.files.each_with_index do |attachment, i|
  html << "</tr><tr>" if i % 3 == 0
  html << "<a href=\"#{attachment}\">File Link</a>"
end
html << "<a href=\"...\">New File Link</a>"

And don't forget to sanitize your strings!

You should try to make more use of the functional approaches in ruby and not try to make it the PHP way... Here's an approach I'd have tried:

# make all file links into a new array converted to html code, append
# a "new file" link
files = object.files.map {|link| '<a href="%s">File Link</a>' % link }
files << ('<a href="%s">New File Link</a>' % "...")

# now break this into slices of 3 wrapped with <td>
files = files.each_slice(3).map {|tr| tr.map {|td| "<td>#{td}</td>" }.join }

# now wrap the rows with <tr>
files = files.map {|tr| "<tr>#{tr}</tr>" }.join

This may look complicated but I think it shows the possibilities and power of mapping functions and block parameters, the code is cleaner by using less helper variables, and it is IMHO more readable / understandable. And best of it: It removes the black magic you need to handle the new file link which almost nobody understands when first looking at the for loop.

BTW: I think you are using Rails although your question asked for Ruby in common. I'd recommend to look at the helpers content_tag and link_to which - combined with the map blocks - make your code even more readable and will handle html escaping for you.

html = ""
object.files.each_slice(3) do |files|
  html << "<tr>"
  files.each do |attachment|
    html << "<a href=\"#{attachment}\">File Link</a>"
  end
  html << "</tr>"
end
html << "<a href=\"...\">New File Link</a>"