nill object error

rubyonrails-talk
1

def grouplist

@currentgroupid=Group.find_by_group_name(params[:group_name]) @currentgroupfriends=GroupFriend.find_all_by_user_id_and_group_id(current_user.id,@currentgroupid)

format.html {redirect_to :back}

end

Please check my controller and help me in solving my problem.

I need to get groupid from the group_name from groups table and The list of friendid s for in the group created by the user which are available in the groupfriends table. My requirement Ex : select friends from groupfriends where userid=current_user.id and groupid=currentgroupid

Please help me in writing the above query in the controller in rails.

Thanks.

2

Ravi Dtv wrote:

def grouplist

@currentgroupid=Group.find_by_group_name(params[:group_name]) @currentgroupfriends=GroupFriend.find_all_by_user_id_and_group_id(current_user.id,@currentgroupid)

format.html {redirect_to :back}

end

What does the log tell you is nil? current_user or @currentgroupid?

a. You're assuming that @currentgroupid will always have a value, which may be okay depending on the source of params[:group_name], which we don't know.

b. What is populating current_user? Is that the source of the nil error?

3

Ar Chron wrote:

Ravi Dtv wrote:

def grouplist

@currentgroupid=Group.find_by_group_name(params[:group_name]) @currentgroupfriends=GroupFriend.find_all_by_user_id_and_group_id(current_user.id,@currentgroupid)

format.html {redirect_to :back}

end

What does the log tell you is nil? current_user or @currentgroupid?

a. You're assuming that @currentgroupid will always have a value, which may be okay depending on the source of params[:group_name], which we don't know.

b. What is populating current_user? Is that the source of the nil error?

Thanks for your reply

def showfriendslist

@currentgroupid=Group.find_by_group_name(params[:group_name]).id @friendsingroup=GroupFriend.find_all_by_user_id_and_group_id(current_user.id, @currentgroupid)

respond_to do |format|   format.html {render :partial => "friendlist" }   format.xml

  end

This is my controller. My current_user is the current logged in user. I can get the groupid value into @currentgroupid.

When I tried in console

@currentgroupid=Group.find_by_group_name('testinggroup')

=> #<Group id: 23, created_at: "2010-05-17 14:00:13", updated_at: "2010-05-17 14:00:13", user_id: 9, group_name: "testinggroup">

@currentgroupid.id

=> 23

@friendsingroup=GroupFriend.find_all_by_user_id_and_group_id('9',@currentgroupid.id )

=> [#<GroupFriend id: 15, created_at: "2010-05-19 04:36:21", updated_at: "2010-05-19 04:36:21", group_id: 23, friend_id: 4, user_id: 9>]

@friendsingroup.id

(irb):42: warning: Object#id will be deprecated; use Object#object_id => -618448038

@friendsingroup.group_id

NoMethodError: undefined method `group_id' for #<Array:0xb64676b4>   from (irb):43

In view I get the following error

RuntimeError in UsersController#showfriendslist

Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id

Please help.. Im new to Ruby on Rails.

Thank you.

end

4

Ar Chron wrote:

Ravi Dtv wrote:

def grouplist

@currentgroupid=Group.find_by_group_name(params[:group_name]) @currentgroupfriends=GroupFriend.find_all_by_user_id_and_group_id(current_user.id,@currentgroupid)

format.html {redirect_to :back}

end

What does the log tell you is nil? current_user or @currentgroupid?

a. You're assuming that @currentgroupid will always have a value, which may be okay depending on the source of params[:group_name], which we don't know.

b. What is populating current_user? Is that the source of the nil error?

Thanks for your reply

def showfriendslist

@currentgroupid=Group.find_by_group_name(params[:group_name]).id @friendsingroup=GroupFriend.find_all_by_user_id_and_group_id(current_user.id, @currentgroupid)

respond_to do |format| format.html {render :partial => "friendlist" } format.xml

end

This is my controller. My current_user is the current logged in user. I can get the groupid value into @currentgroupid.

When I tried in console

@currentgroupid=Group.find_by_group_name('testinggroup')

=> #<Group id: 23, created_at: "2010-05-17 14:00:13", updated_at: "2010-05-17 14:00:13", user_id: 9, group_name: "testinggroup">

@currentgroupid.id

=> 23

@friendsingroup=GroupFriend.find_all_by_user_id_and_group_id('9',@currentgroupid.id )

=> [#<GroupFriend id: 15, created_at: "2010-05-19 04:36:21", updated_at: "2010-05-19 04:36:21", group_id: 23, friend_id: 4, user_id: 9>]

@friendsingroup.id

(irb):42: warning: Object#id will be deprecated; use Object#object_id => -618448038

@friendsingroup.group_id

NoMethodError: undefined method `group_id' for #<Array:0xb64676b4> from (irb):43

That is because @friendsingroup is an array because you have used find_all_by_... The clue is in the error message. It says that class Array has not got a method group_id

In view I get the following error

RuntimeError in UsersController#showfriendslist

Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id

That means that you have used something.id where id is nil. You still have not told us which line in the view is giving the error. Look at the error message and see which line it is, then look to see what id you are using on that line and most likely you will find the nil object. Then you just have to work out why it is nil. In order to avoid your view crashing you could test it for nil and put a message in the view instead of allowing it to crash.

I also suggest also that you have a look at the Rails Guide on debugging. It will show you ways of breaking in to your code to inspect the variables. I use ruby-debug when I have this sort of problem.

Colin

5

Colin Law wrote:

�format.xml "2010-05-17 14:00:13", user_id: 9, group_name: "testinggroup"> �from (irb):43

That is because @friendsingroup is an array because you have used find_all_by_... The clue is in the error message. It says that class Array has not got a method group_id

In view I get the following error

�RuntimeError in UsersController#showfriendslist

Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id

That means that you have used something.id where id is nil. You still have not told us which line in the view is giving the error. Look at the error message and see which line it is, then look to see what id you are using on that line and most likely you will find the nil object. Then you just have to work out why it is nil. In order to avoid your view crashing you could test it for nil and put a message in the view instead of allowing it to crash.

I also suggest also that you have a look at the Rails Guide on debugging. It will show you ways of breaking in to your code to inspect the variables. I use ruby-debug when I have this sort of problem.

Colin

Thanks Colin for the reply.

When debugging i find currentgroupid is nill.

How can I solve this. Possible solutions to pass values form partial to controller.         <% @groups.each do |g| %>    <p> <h5>      <%= link_to_remote g.group_name, :update => "abc", :url => { :controller => "users" , :action => "showfriendslist" } %>

   <%= hidden_field_tag :group_name %> </h5> </p> <% end %>

I can see my groupname displaying in my page, but when I click on my groupname link, Im not able to pass groupname to my controller.

My controller:

def showfriendslist

   @currentgroupid=Group.find_by_group_name(params[:group_name]).id

#@friendsingroup=GroupFriend.find_all_by_user_id_and_group_id(current_user.id,@currentgroupid)

  respond_to do |format|   format.html {render :partial => "friendlist" }

  format.xml   end

end

Please help. Thank you.

6

...> When debugging i find currentgroupid is nill.

How can I solve this. Possible solutions to pass values form partial to controller. <% @groups.each do |g| %> <p> <h5> <%= link_to_remote g.group_name, :update => "abc", :url => { :controller => "users" , :action => "showfriendslist" } %>

<%= hidden_field_tag :group_name %> </h5> </p> <% end %>

I can see my groupname displaying in my page, but when I click on my groupname link, Im not able to pass groupname to my controller.

Using a hidden field does not work as you are not in a form. That is how to do it if you were submitting from a form. Instead just include the name in the url - something like <%= link_to_remote g.group_name, :update => "abc", :url => { :controller => "users" , :action => "showfriendslist", :group_name => g.group_name } %>

Look at the html generated by this to check that it is being included correctly.

Colin

7

Colin Law wrote:

8

I can see my groupname displaying in my page, but when I click on my groupname link, Im not able to pass �groupname to my controller.

Using a hidden field does not work as you are not in a form. That is how to do it if you were submitting from a form. Instead just include the name in the url - something like <%= link_to_remote g.group_name, :update => "abc", :url => { :controller => "users" , :action => "showfriendslist", :group_name => g.group_name } %>

Look at the html generated by this to check that it is being included correctly.

Colin

Thank you Colin

I got the output.

Can you please solve this error for me

undefined method `each' for 4:Fixnum

9

I am sure you can work it out for yourself. Look at the line of code that generates the error, presumably there is a call to 'each' there. The error says that you are trying to call each for the value 4 (which is of type Fixnum), presumably you expected it to be an Array. If you can't see the problem by code inspection use ruby-debug to break in before that line and have a look at the variable you are calling each on.

Colin