<div class="gmail_quote">On 2 April 2012 19:55, Andrew Stewart <span dir="ltr"><<a href="mailto:boss@airbladesoftware.com">boss@airbladesoftware.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im"><br>
On 2 Apr 2012, at 17:05, James Hunt wrote:<br>
> How much more convenient is it though? How much time do you really save by having instance variables by default?<br>
<br>
</div>Compared to the Java way, which is where I came from when I switched to Rails, using `@post` in a view is far more convenient than `((Post) request.getParameter("post"))` (if I recall my Java from 7 years ago correctly).<br>
<br>
Compared to Proffer, I think this:<br>
<br>
class PostsController < ApplicationController<br>
def new<br>
@post = Post.new<br>
end<br>
end<br>
<br>
<%= form_for(@post) do |f| %><br>
...<br>
<% end %><br>
<br>
-- is more convenient than this:<br>
<div class="im"><br>
class PostsController < ApplicationController<br>
include Proffer<br>
def new<br>
proffer :post => Post.new<br>
end<br>
end<br>
<br>
</div> <%= form_for(post) do |f| %><br>
...<br>
<% end %><br>
<br></blockquote><div>The problem that proffer addresses isn't the important problem IMO. The problem is that with Rails it is so easy to get powerful objects without constraints into views where they can be abused. In the above code the Post.new is (probably) such an object. First of all it will be an ActiveRecord object, and more importantly it has no place in the object hierarchy. Avdi Grimm identifies such objects as Lone Wolf's in his Object With Rails book; and I think this lone wolf anti-pattern is quite a profound insight. The thing to do is not get such objects into controllers in the first place. If you are disciplined with your controllers then the standard mechanism used to get things views isn't really a problem. If you write poor controller code, you can still expose with proffer objects that really have no place in a view. The discipline that proffer adds doesn't really address the discipline that controller code needs.</div>
<div><br></div><div>All best</div><div><br></div><div>Andrew</div><div><br></div><div><br></div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I think it consistently saves a little bit of time.<br>
<div class="im"><br>
> It's interesting to think about this the other way: if Rails had never exposed instance variables by default, would you even miss it? Would you have written a gem to add the functionality? How would you justify it?<br>
<br>
</div>I didn't have it before so I wouldn't have been able to miss it. However if it vanished now I would write a gem to replace it...unless it seemed I was in a tiny minority; with Rails it's usually better to go with the flow unless there's a good reason otherwise.<br>
<div class="im"><br>
> In the scheme of all the things you have to do to get a Rails app working, not having instance variables in views seems like a really small thing.<br>
<br>
</div>True, but a lot of Rails' productivity boost comes from the aggregation of many little time-savers.<br>
<div class="im"><br>
> And if you were reaaaaallly desperate, you could do:<br>
><br>
> <% @post = post %><br>
><br>
> at the top of your view and you're back in business! The only difference here is that before you do something like the above, you have to actually think about what you're doing and why before you do it. It's a convention: break it if you want, but know why you're doing it and what it may cost you later on.<br>
<br>
</div>For me, using an instance variable instead of a plain local variable is a fine convention. If I want to share state with a view, I use an instance variable; if I don't want to share state, I use a local variable.<br>
<br>
Cheers,<br>
Andy<br>
<div class="HOEnZb"><div class="h5"><br>
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</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div>------------------------</div>Andrew Premdas<div><a href="http://blog.andrew.premdas.org" target="_blank">blog.andrew.premdas.org</a></div><br>