Help with 'new' form code - 'render' vs 'redirect_to'

Rails
1

Hi, I’m having some trouble to understand the following code:

def new
@user = User.new
@title = “Sign up”
end

def create
@user = User.new(params[:user])
if @user.save
flash[:success] = “Welcome to the Sample App!”
redirect_to @user
else
@title = “Sign up”
@user.password = “”
@user.password_confirmation = “”
render ‘new’
end
end

Since I do ‘@user = User.new’ in the ‘new’ method, why do i need to
do it
again ‘@user = User.new(params[:user])’ instead of
‘@user.update_attributes(params[:user])’ in the ‘create’ method?
Also I don’t get the difference between ‘render’ and ‘redirect_to’,
what
I read was that ‘render’ doesn’t clean out the variables, whereas
‘redirect_to’ does, so back to the first question…

2

On 10 May 2011 21:23, Rodrigo R. [email protected] wrote:

redirect_to @user
else
@title = “Sign up”
@user.password = “”
@user.password_confirmation = “”
render ‘new’
end
end
Since I do ‘@user = User.new’ in the ‘new’ method, why do i need to do it
again ‘@user = User.new(params[:user])’ instead of
‘@user.update_attributes(params[:user])’ in the ‘create’ method?

Each action in the controller is a new request to the web server so
the create action has no knowledge of @user set up in the new action.
It can only go by what is in params.

Also I don’t get the difference between ‘render’ and ‘redirect_to’, what
I read was that ‘render’ doesn’t clean out the variables, whereas
‘redirect_to’ does, so back to the first question…

Render will re-show the ‘new’ page, with the form for filling in the
new user so the user can fix the errors @user still has the values
from the data was submitted last time so the form will show the same
data again. The redirect causes the ‘show’ action to be run for the
user, which results in that user being shown.

Colin

3

On May 10, 2011, at 4:23 PM, Rodrigo R. wrote:

  flash[:success] = "Welcome to the Sample App!"

to do it again ‘@user = User.new(params[:user])’ instead of
‘@user.update_attributes
(params[:user])’ in the ‘create’ method?

Because of the stateless nature of the HTTP protocol. The first
request is for a form. The second request is a post of the filled
form. In between those two, there could be moments or hours or days,
and the server has long since lost interest in that object you create.

In the New method, you use that User.new to spin up the form inputs,
to set your defaults, and that’s about all.

In the Create method, you create a completely different empty user,
fill it with the result of the POST, validate those inputs, and save
if it passes. It’s not really an update at all.

Walter

4

if it has no knowledge of @user in the ‘new’ action, why do I need to do
@user = User.new? What is the point, if it will be lost for other
actions?

I thought that all that i wrote with ‘@’ in ruby was an instance
variable,
meaning it is accessible to the whole instance, meaning any of its
methods.

5

On 10 May 2011, at 21:32, Colin L. [email protected] wrote:

  flash[:success] = "Welcome to the Sample App!"

‘@user.update_attributes(params[:user])’ in the ‘create’ method?
new user so the user can fix the errors @user still has the values
from the data was submitted last time so the form will show the same
data again. The redirect causes the ‘show’ action to be run for the
user, which results in that user being shown.

To be complete explicit, calling render just tells rails which template
to use, whereas redirect_to tells the browser that they should make a
separate http request to the specified location

Fred

6

On Mon, May 16, 2011 at 12:46 PM, Rodrigo R.
[email protected]wrote:

if it has no knowledge of @user in the ‘new’ action, why do I need to do
@user = User.new? What is the point, if it will be lost for other actions?

@user is used in @user = User.new so that you have your new user object
available for the form builder on the view.

I thought that all that i wrote with ‘@’ in ruby was an instance variable,
meaning it is accessible to the whole instance, meaning any of its methods.

It is but as others have mentioned before, and maybe in other words:
whatever you create only applies to the current request. The next time
the
browser hits the controller, it is fresh and you start over (and maybe
use
params or sessions to keep the state as needed).

7

Now I think I got it, thank you.

I need @user = User.new for the line ‘form_for(@user)’ in the view
‘new.html.erb’ right?

And what is the point of making ‘@user’ instead of ‘user’ (local
variable)
if it will be lost anyway for other requests?

8

Thank you.

9

On Mon, May 16, 2011 at 1:04 PM, Rodrigo R.
[email protected]wrote:

Now I think I got it, thank you.

I need @user = User.new for the line ‘form_for(@user)’ in the view
‘new.html.erb’ right?

Correct

And what is the point of making ‘@user’ instead of ‘user’ (local variable)
if it will be lost anyway for other requests?

Try it and you will understand… if you make it ‘user’ the form wont
see
it. Remember, ‘user’ inside a controller method is local to that method.
If
you have any class and want to make a variable visible for the whole
class,
not just the immediate method, you need to use @var (or another method).
Think of the view as being in the same class as the controller but not
inside the controller method.