guys! I'm trying to make right architecture decision:
I need to hide from user of my site some fields of other users by default. So not to bother with filtering the fields in views I want to not load those fields at all, like:
default_scope -> { select(column_names - FILTERED_PARAMS) }
the rest of fields should be loaded explicitly in special cases.
The problem is that once code refers to the missing fields nomethod error shows up. I tried to meta-program those fields but fruitless this far. It seems to me that this approach doesn't fit to the AR object life-cycle.
Have you ever implemented such functionality if so what pattern have you chosen?
From my experience the best decision would be not to filter these params on the query with select, but to filter what parameters are actually sent to the user. my_model.as_json (with given param filtering options) is a simple solution for that, but for more advanced uses I would advise Rabl gem
https://github.com/nesquena/rabl
That way you have more control over which params are returned even in very advanced cases in a model-view-controller manner.
Related
In my Ruby on Rails project, I have a mailer that basically prepares a daily digest of things that happened in the system for a given user. In the mailer controller, I am gathering all the relevant records from the various models according to some common pattern (within a certain date, not authored by this user, not flagged, etc) and with minor differences from model to model.
There are half a dozen of models involved here (and counting), and most of them have unified column names for certain things (like date of publishing, or whether an item is flagged by admin or not). Hence, the 'where's that go into query are mostly the same. There are minor differences in conditions, but at least 2 or 3 conditions are exactly the same. I easily assume there may be even more similar conditions between models, since we are just starting the feature and haven't figured out the eventual shape of the data yet.
I basically chain the 'where' calls upon each model. It irritates me to have 6 lines of code so close to each other, spanning so far to the right of my code editor, and yet so similar. I am dreaded by the idea that at some point we will have to change one of the 'core' conditions, munging with that many lines of code all at once.
What I'd love to do is to move a core set of conditions that goes into each query into some sort of Proc or whatever, then simply call it upon each model like a scope, and after that continue the 'where' chain with model-specific conditions. Much like a scope on each model.
What I am struggling with is how exactly to do that, while keeping the code inside mailer. I certainly know that I can declare a complex scope inside a concern, then mix it into my models and start each of queries with that scope. However, this way the logic will go away from the mailer into an uncharted territory of model concerns, and also it will complicate each model with a scope that is currently only needed for one little mailer in a huge system. Also, for some queries, a set of details from User model is required for a query, and I don't want each of my models to handle User.
I like the way scopes are defined in the Active Record models via lambdas (like scope :pending, -> { where(approved: [nil, false]) }), and was looking for a way to use similar syntax outside model class and inside my mailer method (possibly with a tap or something like that), but I haven't found any good examples of such an approach.
So, is it possible to achieve? Can I collect the core 'where' calls inside some variable in my mailer method and apply them to many models, while still being able to continue the where chain after that?
The beauty of Arel, the technology behind ActiveRecord query-building, is it's all completely composable, using ordinary ruby.
Do I understand your question right that this is what you want to do?
def add_on_something(arel_scope)
arel_scope.where("magic = true").where("something = 1")
end
add_on_something(User).where("more").order("whatever").limit(10)
add_on_something( Project.where("whatever") ).order("something")
Just ordinary ruby method will do it, you don't need a special AR feature. Because AR scopes are already composable.
You could do something like:
#report_a = default_scope(ModelA)
#report_b = default_scope(ModelB)
private
def default_scope(model)
model.
where(approved: [nil, false]).
order(:created_at)
# ...
end
Here's my challenge. I have a key/value set that I want to tie to a model. These are my specific requirements:
I want the hash to be stored as a serialized JSON object in the model's table instead of in a separate table
I want to be able to pre-define the valid keys within the model itself
I want to be able to set a strong type for each key and automatically perform validations. I don't want to have to write validation functions for each individual attribute unless it needs a validation out of the basic data type scope.
I would LOVE to be able to magically access the attributes inside a form generator (f.input :my_key) and have the form generator recognize that :my_key is of type :boolean and create a checkbox instead of a generic text input. The same for other data types.
There are a few different ways to solve this problem, and lots of opinions for both. I read over this answer from 5 years ago:
Best approach to save user preferences?
It seems that many/most of those plugins have been abandoned. Anything else come out in the last 5 years that matches my criteria?
Your question is a bit open-ended, but as far as I can see your needs, they should be met with using Hashie gem.
I'm not sure what's the best approach in my situation, I would like an opinion.
My situation is:
I have a "Ticket" model, having several fields of many kinds: text, numerical and associations. Tickets support comments through the acts_as_commentable gem.
The tickets are generated by users, who can comment and modify their own tickets.
Because the fields of a ticket can change over time I would like to allow my users to modify several of them. What I need though is to keep a commented history of all the changes, so that at any moment they can see in a ticket what, why and when was changed, in the comment, timestamp and list of changes that they can see together with the comment.
I was thinking to solve this by generating a "TicketUpdate" model, have the TicketUpdates generated in the Comments form (using fields_for and accepts_nested_attributes_for).
Basically the user could select in a drop down list (i.e. a select tag) the field they want to change, changing the value of the drop down would trigger an event to show an appropriate input field (input for the text and numeric fields, select for the associations) with the old value pre-populated
I could intercept the TicketUpdates in the "comment/create" controller performing the updates.
This approach would look nice and sweet to the user, but I don't see how to implement in a neat or DRY way.
Because ticket has many fields and they are mixed decimals and associations, I would have to implement specific logic for each field, both in the view and in the controller.
I'm not sure if there's maybe a better approach, or there's actually any gem or trick to get this done easily.
anyone got anything to recommend me here?
I'm using rails 3.2.8.
I want to have a site that is a simple blog so I created a model:
class Post < ActiveRecord::Base
attr_accessible :title, :body
end
I want to use Markdown but without HTML tags. I also want always to keep database clean and my idea is to use before_save()/before_update() callbacks to sanitise my input and escape HTML.
I don't care about caching and performance therefore I always want to render post when needed. My idea is toadd following to the model:
def body_as_html
html_from_markdown(body)
end
What do you think of such design? MVC and ActiveRecord are new for me and I am not sure of used callback.
I see nothing obvious wrong with that method. Caching is a very simple thing to enable if performance becomes an issue... the important thing to make caching useful is to reduce or eliminate the dynamic content on the page, so that the cache doesn't constantly get obsolete. If you're just showing the blog post, then the cache only needs to be regenerated if the blog changes, or perhaps if someone adds a comment (if you have comments).
My general rule of thumb is to keep the data in your database as "pure" as possible, and do any sanitization, rendering, escaping or general munging as close to the user as possible - typically in a helper method or the view, in a Rails app.
This has served me well for several reasons:
Different representations of your data may have display requirements - if you implement a console interface at some point, you won't want to have all that html sanitization.
Keeping all munging as far out from the database as possible makes it clear whose responsibility it is to sanitize. Many tools or new developers maintaining your code may not realize that strings are already sanitized, leading to double-escaping and other formatting ugliness. This also applies to the "different representations" problem, as things can end up escaped in multiple different ways.
When you look in your database by hand, which will end up happening from time to time, it's nice to see things in their un-munged form.
So, to address your specific project, I would suggest having your users enter their text as Markdown and storing it straight in to the database, without the before_save hook (which, as an aside, would be called on creation or update, so you wouldn't also need a before_update hook unless there was something specific that you wanted on update but not creation). I would then create a helper method, maybe santize_markdown, to do your sanitization. You could then call your helper method on the raw markdown, and generate your body html from the sanitized markdown. This could go in the view or in another helper method according to your taste and how many different places you were doing it, but I probably wouldn't put it in the model since it's so display-specific.
Is it possible to use select fields with nested object forms feature of Rails 2.3?
Example:
Suppose you have a Article model, Category model, and a ArticleCategories join model. Article has_many Categories through ArticleCategories.
On our Edit Article form, you want to have an HTML select list of all the available categories. The user can select one or more Category names to assign to the Article (multiple select is enabled).
There are lots of ways to do this, but I'm wondering if there is a simple way to accomplish this using the nested objects feature. What would the form look like in your view?
Check out the nested form example from Github:
http://github.com/alloy/complex-form-examples
It's been a while since I looked at it, so I'm not sure if it covers exactly what you wanna do, but its a nice source for ideas / patterns.
Assuming you have defined the models and their relationships so you can do this:
#art = Article.find(article_id)
#art.categories # returns list of category objects this article is assigned to.
Then I usually use http://trendwork.kmf.de/175
You need to copy the JavaScript file into public/javascripts but after that you can just create the form element with something like:
swapselect(:article,#art,:categories,Category.find(:all).map { |cat| [cat.name, cat.id] })
(I would tend to wrap that in a helper to make the call even cleaner)
One small gotcha is that for very long lists it can run a little slow in IE6 because there's quite a lot of appendChild calls in the js which is notorioulsy slow in IE6
Update: Apologies. This doesn't really answer your original question, which was specifically about the Rails 2.3 feature. The swapselect option is version independent and doesn't make use of newer Rails functionality.