Question on the "common way" to code

Rails
1

So I posted last week asking about new learning resources. I watched
the lynda.com RoR videos, and now I just started reading the Ruby for
Rails book. Both of these sources code in different ways, and I was
wondering which way is most common. In other words, is one of these
ways frowned upon in the Rails community? Keep in mind that these are
rather specific examples and not necessarily complete lines of code.

  1. First is how things are read from a database, or more specifically,
    sorting. One does this
    @albums = Album.find(:all, :order => “title ASC”)
    while the other does this
    @composers = Composer.find(:all).sort_by{|c| [c.last_name,
    c.first_name]}

  2. Looping.
    <% for composer in @composers -%>
    and
    @composers.each do |composer|

  3. dynamic links
    link_to(composer.first_name + " " + composer.last_name
    and
    link_to(“#{composer.first_name} #{composer.last_name}”

In all cases I prefer the first (lynda.com) method, either because
it’s shorter or because it requires less symbols. The Ruby for Rails
method seems to be a lot more object focused. So which of these do
you see more often or is the common way? Or does it not matter?

2

(1) It depends. The first allows the database to do the sorting,
which is almost always a good thing. The second performs the sorting
in memory, and is thus likely to be slower. I’ve seldom seen the
second method employed in real code because databases are so good at
sorting.

(2) In RHTML, many people use <% for composer in @composers -%> I
don’t. I don’t use for in Ruby. So my looping code is usually <%
@composers.each do |composer| -%>. That said, it is often cleaner to
render collections in partials. That would look like this: <%=
render :partiai => ‘composer’, :collection => @composers %>.

(3) Whatever works. Either works fine, both are ugly but necessary.
Better, in your model do this:

def full_name
first_name + last_name
end

Then in your view, you can just write:

<%= link_to composer.full_name, composers_url(composer) %>

Just some thoughts.

3

s.ross wrote:

(3) Whatever works. Either works fine, both are ugly but necessary.
Better, in your model do this:

def full_name
first_name + last_name
end

The question was “…” vs. model.method + " " + model.method. I agree you
should put these kinds of function in the model or in a helper.

  1. dynamic links
    link_to(composer.first_name + " " + composer.last_name
    and
    link_to("#{composer.first_name} #{composer.last_name}"

Personally I usually prefer the second alternative as I find it easier
to read. But that’s just a matter of taste.

–
Cheers,

  • Jacob A.
4

Hi –

On Sat, 21 Jul 2007, nemesis256 wrote:

@albums = Album.find(:all, :order => “title ASC”)
link_to(composer.first_name + " " + composer.last_name
and
link_to(“#{composer.first_name} #{composer.last_name}”

In all cases I prefer the first (lynda.com) method, either because
it’s shorter or because it requires less symbols. The Ruby for Rails
method seems to be a lot more object focused. So which of these do
you see more often or is the common way? Or does it not matter?

Going from bottom to top:

Using string interpolation is slightly more efficient because it
avoids creating a lot of intermediate string objects.

“each” is generally considered more idiomatic Ruby than “for”. for is
really just sugar-coating for each:

irb(main):018:0> for a in nil; end
NoMethodError: undefined method `each’ for nil:NilClass
^^^^

Queries are a little more complicated. There are, as you point out,
examples in my book where you could use :order (and probably other
things) – and I certainly wouldn’t argue against it, though I’ve also
seen people devote a lot of development time to fine-tuning big SQL
statements when a bit of Ruby would have done the same thing, even if
at some point down the road it ended up getting optimized into SQL.
So you can be creative about what role(s) you want the Ruby techniques
to play (or not play).

One rule of thumb that I try to follow is never to take out too many
records, just for the sake of making it easy to manipulate them in
Ruby. So, for example, I’d avoid this:

Item.find(:all).select {|i| i.number < 100 }

since that’s liable to pull out some huge number of records and then
throw most of them away. (I can’t remember if there are examples like
that in my book… but never mind :slight_smile: But I would certain do things
like this:

Item.find(:all, :conditions => “number < 100”).sort_by {|item|
item.description.sub(/^(a|the) /i, “”)
}

David

–

5

nemesis256 wrote:

  1. dynamic links
    link_to(composer.first_name + " " + composer.last_name
    and
    link_to("#{composer.first_name} #{composer.last_name}"

To my knowledge, there is a difference between those two expressions :
the second one requires more processing than the first one, because of
the double quotes.

#{} evalutes what’s inside of the brackets and the result is transformed
into a string. Because #{var} does not return “the content of var”, but
“the result of the expression var transformed into a string”.
So, if composer.first_name returns a string already, you don’t have to
transform it again in a string.

Another example. If you define number = 5, you can use
“#{number} blabla”
as well as
number.to_s + ‘blabla’
There you can see where lies the difference. For numbers, you have to
use .to_s if you use concatenate (+), a transformation that isn’t needed
for your composer.first_name (apparently).

Besides, double quotes means that the whole expression will be parsed to
look not only for #{}, but also for other escape caracters like “\n”.
This means more processing.

So, the first solution is less redundant (with maybe some performance
effects?), and the second is more readable. Make your choice.

Please, do correct me if I’m wrong, since I started RoR less than a week
ago :slight_smile:

6

Hi –

On Sat, 21 Jul 2007, s.ross wrote:

(3) Whatever works. Either works fine, both are ugly but necessary.
Better, in your model do this:

def full_name
first_name + last_name
end

Then in your view, you can just write:

<%= link_to composer.full_name, composers_url(composer) %>

That still leaves the question of how to define full_name (with + or
with string interpolation), though. Some informal benchmarking
suggests, not too surprisingly, that if you’re adding just two
strings, the adding might be faster, but if you’re adding repeatedly:

title + " " + first_name + middle_name + last_name

then there’s a tipping point at which interpolation is faster.

David

–