why link_to doesn't work(rails)

Question

I have model User. And one of controller methods is

 def view_messages
    @user = User.find(params[:id])
    @message=Message.new
    @[email protected]
  end

Also i have model Message , and one of parametres of this model is user_from:integer

view_messages view have

render :partial => 'messages/message', :collection => @messages

and _message.haml have

= content_tag_for(:li,message) do
  %p
    From:
    =link_to User.find(message.user_from).name,User.find(message.user_from)

it writes an error

Couldn't find User without an ID

but if i want to print it like

 = content_tag_for(:li,message) do
      %p
        From:
        =message.user_from

it print it ( for exaple it prints 2) , so why it cant find user with id 2 if i have this user? What i am doing wrong? Thanks in advance

How does @user.messages work? I guess it's not a has_many relation, judging from your code. — Leonid Shevtsov
– Leonid Shevtsov, Commented Oct 30, 2011 at 14:59

Leonid Shevtsov · Accepted Answer · 2011-10-30 14:59:30Z

2

General issues:

user_from should be user_from_id, by Rails convention
Then you should have a belongs_to relation:
```
class Message
  belongs_to :user_from
end
```
which will automatically pull the user from the database
Then you can refer to the user as an attribute of Message
```
link_to @message.user_from.name, @message.user_from
```

Check all of the Message records. One of them probably has no user_from, and causes the error.

answered Oct 30, 2011 at 14:59

Leonid Shevtsov

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3 Comments

Pavel Over a year ago

thanks. i am newbie / i will try to follow all ruby conventions. You were right,i needed to reset my database, cause old messages didnt had parameter :user_from

apneadiving Over a year ago

and you should do @user = User.find(params[:id]).include(:messages)

apneadiving Over a year ago

generally speaking your current infrastructure is terrible in terms of performance and db queries

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