The code below displays peferctly what i want to accomplish (show store name and item name).But when i subtitute #onedeal=#deal.find_with_ids(62) with #onedeal=#deal.find(params[:id]) i get an error Couldn't find Deal without an ID.What method should i use to fetch deal ID dynamically?The relationship between the Deal and store model is has many :through.
controller
#deal=#city.deals
#onedeal=#deal.find_with_ids(62)
#store=#onedeal.stores.first(params[:store_id])
view
<% #deal.each do |deal| %>
<%=deal.item_name %>
<%end%>
<%=#store.store_name %>
That error means that params[:id] is empty. Check your params hash to see what it contains, and verify that your action is getting the input it expects.
You are absolutely using the .find method as intended, so I don't think that's the issue.
What about
Deal.find(params[:id]) rescue nil
Related
In my method via some calculations a get data, then i need to view it in view, but if write
#ar.each do |a|
when i have only one record i get error, also when i have one error each is bad idea. So how to do this this?
So i have such code in method:
non_original = []
#articles.each do |a|
non_original << get_non_tecdoc("LA44", 1, "KNECHT")
end
#non_original = non_original
get_non_tecdoc returns object, or nothing...
So in view i have:
-#non_original.each do |no|
=no.brand
=no.description
=no.price
=no.quantity
But what to do if #non_original has one record, then #non_original.each gives error. So how to do check in view? If #non_original has one record, than simple #non_original.brand etc, but if more than one, than use each loop?
This will work with #ar as a single value as well as an array:
Array(#ar).each do |a|
p a
end
This Array is a method on Kernel.
<%= debug #ar %>
This will give you a nice YAML format to look at in your view (assuming ERB).
EDIT: I believe this is what you want, since you're not interested in debugging.
In your controller, use the splat operator to convert a singleton element to an array (it doesn't modify arrays):
#ar = *#ar
Then #ar.each will work as expected in your view.
Alternatively, you could check in your view:
<% if #ar.is_a?(Array) %>
<% #ar.each ... %>
<% else %>
<%= #ar %>
<% end%>
Why don't you try using #ar.inspect and output it to the console to see the instance variables contents.
As long as #ar is an array you should not get a error. If you are returning one record change it to an array with one record.
If you are using active record query interface like the "where" clause; it will return an array with 0 or more active_record objects. If you use find it will return one instance of an active_record object.
So if your method that queries is using the active record where clause #ar should always return an array.
Please try this:
Tablename.find_by_table_id
Example:
if account_id is 10 then, take following example,
#getResults = Account.find_by_account_id(10)
It will gives single record.
we can get values using #getResults.id,#getResults.name ....like wise.
in my controller I am collecting data (into a hash) like this (note that I do not have a BillingAddress model in my app, #billing_address is standard ruby hash
#billing_address = params[:billing_address]
my view is laid out like this
<%= text_field_tag 'billing_address[phone]' %>
I want to show the previous value that user entered (in case of errors), like this:
<%= text_field_tag 'billing_address[phone]', #billing_address['phone'] %>
however, this gives me an exception saying I am trying to access nil, ideas?
I guess params[:billing_address] is nil.
Try to assign empty hash if it is.
#billing_address = params[:billing_address] || {}
This is not the Rails way of showing previous values in case of error. Check this screencast to get idea on how to handle errors better way.
I have the following code in a layout:
Posted <%=time_ago_in_words post.created_at %> ago
<% if post.has_tag != nil %>
in the <%= post.get_first_tag.name %> category
<% end %>
And the following code in the post model which is inheriting form ActiveRecord::Base
def has_tag
!self.tags.empty?
end
def get_first_tag
self.tags[0]
end
Tags is also inherited from ActiveRecord::Base and Post 'has_many' Tags
Firstly: Is this the best way of checking if the post object has at least 1 associate tag attribute.
Secondly: Should I be putting this logic into a helper method?
Thirdly: Why doesn't the following work (it returns a # where the tags should be):
in the <%= post.tags.to_sentence %> category,
I guess its because tags aren't actually stored as an array attribute, but i don't really know.
This is a perfectly good way of checking if there are tags or not. However, self.tags.empty? will return true or false so post.has_tag will never be nil.
It's worth noting that, in ruby, it is common to name methods that return true or false with a question mark. So post.has_tag? would be a better name for your method (like the empty? method for the tags).
This sort of method belongs in the model class rather than a helper as it is not specific to the view layer; you might want to call this method from other model classes, for example.
The reason you are getting # instead of your tag names is that you are trying to convert a collection of tags to a sentence and you need instead to convert the names of the tags to a sentence. You should be able to do
post.tags.map(&:name).to_sentence
which will take the names of the tags and turn them into a sentence.
For one thing, you probably need
<% if post.has_tag %>
instead of
<% if post.has_tag != nil %>
In your definition, has_tag should never return nil, and thus 'in the...' part will always be shown.
Generally, your idea seems fine to me: I often add helpers like these to models.
I want to show a post author's name; <% #post.author.name %> works unless author is nil. So I either use unless #post.author.nil? or add a author_name method that checks for nil as in <% #post.author_name %>. The latter I try to avoid.
The problem is that I may need to add/remove words depending on whether there is a value or not. For instance, "Posted on 1/2/3 by " would be the content if I simply display nil. I need to remove the " by " if author is nil.
Null object pattern is one way to avoid this. In your class:
def author
super || build_author
end
This way you will get an empty author no matter what. However, since you don't actually want to have an empty object sometimes when you do expect nil, you can use presenter of some kind.
class PostPresenter
def initialize(post)
#post = post
end
def post_author
(#post.author && #post.author.name) || 'Anonymous'
end
end
Another way is using try, as in #post.author.try(:name), if you can get used to that.
You can use try:
<%= #post.author.try(:name) %>
It will attempt to call the name method on #post.author if it is non-nil. Otherwise it will return nil, and no exception will be raised.
Answer to your second question: In principle there is nothing wrong with the following:
<% if #post.author %>
written by <%= #post.author.name %>
<% end %>
or
<%= "written by #{#post.author.name}" if #post.author %>
But if this is a recurring pattern, you might want to write a helper method for it.
# app/helpers/authors_helper.rb or app/helpers/people_helper.rb
class AuthorsHelper
def written_by(author)
"written by #{author.name}" if author
end
end
# in your views
<%= written_by(#post.author) %>
Write a method which accepts any variable and checks to see if it is nuil first, and if it is not displays it. Then you only have to write one method.
I found your question interesting as I have often come across similar situations, so I thought I'd try out making my first Rails plugin.
I'm afraid I haven't put in any tests yet but you can try it out http://github.com/reubenmallaby/acts_as_nothing (I'm using Ruby 1.9.1 so let me know if you get any problems in the comments or on Github!)
I would like to display a line of text only if an object called #foo is set.
In my view, I'm trying something like this:
<% if !#foo.new_record? || !#foo.nil? %>
Foo is not a new record or nil
<% end %>
But this fails, returning You have a nil object when you didn't expect it!
I'm pretty sure this happens because of the new_record? method.
How do I check if something is not a new record or nil without causing an error?
In PHP, it would be achieved by asking if(!empty($foo)) but even the empty? method in rails causes the same error to be returned.
Any ideas?
How about:
<% if !#foo.nil? && !#foo.new_record? %>
Hello!
<% end %>
First off, you need to be using AND logic rather than OR logic here, since any ActiveRecord object meets at least one the requirements of "not nil" or "not a new record".
Second, checking for nil first ensures that the second check isn't run if the first one fails. The error is thrown because you can't use #new_record? on an object that doesn't support it, so checking for nil first ensures that that method is never run on a nil.
Let me throw another answer just for fun.
unless #foo.nil? or #foo.new_record?
"Hello"
end
You might be interested in these as well:
<%= #foo.text if #foo.present? %>
or
<%= #foo.text unless #foo.blank? %>
I would check by if #foo && #foo.id. This checks that there is a #foo activerecord object and makes sure the id field is not empty. If the id field is empty, that means it's not a record in the database yet. I assume you are using id field in the table.
The simple way is
<% if !#foo.try(:new_record) %>
Hello!
<% end %>
Is there a reason why this object might be nil when it gets to the view? Sometimes adding conditional logic like this in the view can be a sign that something could be refactored and you are just masking a bigger problem.
I much prefer to use the andand gem for these checks.
if #foo.andand.id
"Hello!"
end
The call to .id will only be made on non-nil objects.