Rails - Format number as currency format in the Getter - ruby-on-rails

I am making a simple retail commerce solution, where there are prices in a few different models. These prices contribute to a total price. Imagine paying $0.30 more for selecting a topping for your yogurt.
When I set the price field to
t.decimal :price, precision:8, scale:2
The database stores 6.50 as 6.5. I know in the standard rails way, you call number_to_currency(price) to get the formatted value in the Views. I need to programmatically call the price field as well formatted string, i.e. $6.50 a few places that are not directly part of the View. Also, my needs are simple (no currency conversion etc), I prefer to have the price formatted universally in the model without repeated calling number_to_currency in views.
Is there a good way I can modify my getter for price such that it always returns two decimal place with a dollar sign, i.e. $6.50 when it's called?
Thanks in advance.
UPDATE
Thanks everyone.
I've elected to use Alex's approach because it seems very 'hackish' to do the includes just for formatting the number. Using his approach, I did:
def price_change=(val)
write_attribute :price_change, val.to_s.gsub(/[\$]/,'').to_d
end
def price_change
"$%.2f" % self[:price_change]
end
Cheers.
UPDATE 2
Caveat Emptor. Once you do this, you lose the ability to do operations to the number because it's now a string.
Please beware if anyone is facing the same problem as me.

Just add a method in your model which is named like your attribute in the database like:
def price
"$%.2f" % self[:price]
end
which gives you full control over the formatting or use the Rails provided helper method
def price
ActionController::Base.helpers.number_to_currency(self[:price])
end
this should do the trick.
hope it helps!

You can use the helpers module, but you should not include the whole module, because it includes a lot of methods which you may not really need or overrides some of yours. But you can use them directly:
ActionController::Base.helpers.number_to_currency(6.5)
#=> "$6.50"
You could also define a method for the helpers, so you can easily use them.
def helpers
ActionController::Base.helpers
end
"#{helpers.number_to_currency(6.5)}"
Have a look at this railscast

I'd suggest going with a Presenter approach, like Draper (see this reailscast) does.
Another solution would be to implement your own method in your model, i.e. formatted_price and do the formatting on your own, (i.e. with the ActionView::Helpers::NumberHelper module). But since models represent the plain data in your rails application, it's kinda shady doing something like this and it interferes with the convention over configuration approach, I think.

try
include ActionView::Helpers::NumberHelper
to your model

Related

How to return virtual attribute in Rails depending on session/cookie

I have a model Book. It has properties - name, author, price.
Also, I have currency switcher on the site. I want to format price depending on currency, selected by the user.
Ruby has number_to_currency function, but it is not that I want, because I need special formatting of the price (for russian we have: 1 рубль, 2 рубля, 5 рублей).
So, I made the virtual attribute price_formatted.
def price_formatted
case cookie[:currency]
when 'usd'
'<span>$'+price.to_s+'</span>'
when 'eur'
'<span>€'+price.to_s+'</span>'
else
'<span>'+price.to_s+'</span> '+Russian.p(price, 'рубля', 'рублей', 'рублей')
end
end
Russian.p makes russian pluralization for numbers. The error is that in price_formatted function cookie is not defined.
P.S. If there is another "right" way to make this thing work - please, teach me.
I think you should pass cookie[:currency] value as a parameter to this helper method.
It makes much more sense, actually: helper methods shouldn't know anything about user cookie, try to keep them as pure as possible!
EDIT: oh, is it a model method? You call it virtual attribute, so I assume so. You should convert it to a view helper then. It makes no sense to have presentational logic inside the model class. Create book_helper.rb under helpers folder, and put that method inside it.
Instead of defining a virtual attribute in the model, i prefer to use the decorator pattern which control how an attribute is going to be display in the view. You can take a look at this gem https://github.com/drapergem/draper. Inside draper, you can access cookie, session and so on.

How do you use multiple form fields to interact with a single method in rails?

I have a model which has start_at and end_at attributes. In the form for the end-user, I am displaying start_at using the standard datetime_select, but I'd rather not have a second datetime select presented to the user. I'm hoping I can create two fields that represent a duration; one for hours, the other for minutes. My question is, how in my view do I use form helpers to automatically fill in the fields when editing an existing entry. Furthermore, how would I connect that to the model and subsequently save the recording using the real attribute, end_at?
Thanks in advance for any advice you can give!
I have to do this a bunch and i've been doing the following:
Use the FormTagHelper versions of the calls for the field to be handled specially.
In the controller, read the form_tag values out of the params object.
delete the extra values:
params[:examplemodelname].delete :distance if params[:examplemodelname].has_key? :distance
put the 'real' values into the params object (in your example, ends_at)
call ExampleModelName.new(params[:examplemodelname]) or #examplemodelname.update_attributes(params[:examplemodelname]) as per usual.
Wouldn't logic like this be better
suited for the model? Fat model,
skinny controller?
I think this is absolutely right. I despise using a controller for stuff like this. In my opinion, controllers are best used for a few things:
Shuffling data between views and models, ala CRUD operations
Access control (usually with before_filters)
Support to fancy UI actions (multiple select, wizards, etc)
Of course everyone has to find their own balance, but I find "making an exception" for something like this tends to lead to exceptions everywhere. Not to mention the controller logic is harder to test.
To answer your question: you should simply define virtual attributes in your model that help you convert between start_at and a duration. Something like:
# Return the duration in seconds. Will look different if you want to use
# multiparameter assignment (which you definitely should consider)
def duration
(end_at - start_at).seconds
end
# Store the duration as an instance variable. Might need to use multiparameter
# assignment if you use a time_select() in the view.
def duration=(arg)
#duration = arg
end
before_save :set_end_at
def set_end_at
end_at = start_at + #duration.seconds
end
I'd usually set the actual attribute in a before_save to avoid any race conditions from the form assignment. You have no guarantee that start_at will get assigned before or after duration, and that can introduce bugs in your otherwise good logic.

How to iterate ActiveRecord Attributes, including attr_accessor methods

I've looked everywhere for an elegant solution. The essential problem seems to be that ActiveRecord attributes that map to database columns are handled completely differently in ActiveRecord::Base than attr_accessor methods.
I would like to do something like:
model.attribute_names.each do |name|
# do stuff
end
in a way that also includes attr_accessor fields, but not any other instance methods. I know this in not built-in, but what is the most elegant way to do it?
You can't really solve this. You can approximate a hack, but it's not something that will ever work nicely.
model.attribute_names should get you all the ActiveRecord ones, but the attr_accessor fields are not fields. They are just ordinary ruby methods, and the only way to get them is with model.instance_methods.
Idea 1
You could do model.attribute_names + model.instance_methods, but then you'd have to filter out all your other normal ruby methods initialize, save, etc which would be impractical.
To help filter the instance_methods you could match them up against model.instance_variables (you'd have to account for the # sign in the instance variables manually), but the problem with this is that instance variables don't actually exist at all until they are first assigned.
Idea 2
In your environment.rb, before anything else ever gets loaded, define your own self.attr_accessor in ActiveRecord::Base. This could then wrap the underlying attr_accessor but also save the attribute names to a private list. Then you'd be able to pull out of this list later on. However I'd advise against this... monkey-patching core language facilities like attr_accessor is guaranteed to bring you a lot of pain.
Idea 3
Define your own custom_attr_accessor in ActiveRecord::Base, which does the same thing as Idea 2, and use it in your code where you want to be able to retrieve the attribute names. This would be safe as you won't be clobbering the built-in attr_accessor method any more, but you'll have to change all your code to use custom_attr_accessor where neccessary
I guess in summary, what are you trying to do that needs to know about all the attr_accessor fields? Try look at your problem from a different angle if you can.
I came here looking to do the same thing, and found out it was the wrong approach altogether thanks to Orion's answer.
Incase anyone else's use case is similar to mine, here's my solution. I was using attr_accessor to add extra properties to the models after querying them from ActiveRecord. I then wanted to output the results as JSON etc.
A better solution is to first convert the Models from ActiveRecord into regular hashes, and then add the attr_accessor properties as regular hash keys.
Example:
model_hash = model_from_activerecord.attributes.to_options
model_hash[:key] = value
The solution I came up with for myself builds upon Orion Edwards' answer.
The code:
klass_attributes = klass.column_names + klass.instance_methods(false).
map(&:to_s).keep_if{|a| a.include?('=')}.map{|a| a.sub('=', '')}
The breakdown:
klass.instance_methods(false) brings back only instance methods, and not inherited methods.
map(&:to_s) converts the array of symbols into an array of strings so we can use the include? method. Also needed to merge with array of strings returned by column_names.
keep_if{|a| a.include?('=')} will remove all strings within the array that do not have an equals sign. This was important, since I noticed that attr_accessor attributes all had '='. Ex: 'app_url' vs 'login_url='
map{|a| a.sub('=', '')} is the final piece that then removes the '=' from each string in the array.
You end up with an array of strings that represent attributes, including attr_accessor attributes.

Best practice for converting integer value column to string representation

Lets say you have a model like the following:
class Stock < ActiveRecord::Base
# Positions
BUY = 1
SELL = 2
end
And in that class as an attribute of type integer called 'position' that can hold any of the above values. What is the Rails best practice for converting those integer values into human readable strings?
a) Use a helper method, but then you're force to make sure that you keep the helper method and model in sync
def stock_position_to_s(position)
case position
when Stock::BUY
'buy'
when Stock::SELL
'sell'
end
''
end
b) Create a method in the model, which sort of breaks a clean MVC approach.
class Stock < ActiveRecord::Base
def position_as_string
...snip
end
end
c) A newer way using the new I18N stuff in Rails 2.2?
Just curious what other people are doing when they have an integer column in the database that needs to be output as a user friendly string.
Thanks,
Kenny
Sounds to me like something that belongs in the views as it is a presentation issue.
If it is used widely, then in a helper method for DRY purposes, and use I18N if you need it.
Try out something like this
class Stock < ActiveRecord::Base
##positions => {"Buy" => 1, "Sell" => 2}
cattr_reader :positions
validates_inclusion_of :position, :in => positions.values
end
It lets you to save position as an integer, as well as use select helpers easily.
Of course, views are still a problem. You might want to either use helpers or create position_name for this purpose method
class Stock < ActiveRecord::Base
##positions => {"Buy" => 1, "Sell" => 2}
cattr_reader :positions
validates_inclusion_of :position, :in => positions.values
def position_name
positions.index(position)
end
end
Is there a good reason for the app be converting the integer to the human readable string programmatically?
I would make the positions objects which have a position integer attribute and a name attribute.
Then you can just do
stock.position.name
#HermanD: I think it's a lot better to store the values in an integer column rather than a string column for numerous reasons.
It saves database space.
Easier/faster to index on an integer than a string.
Your not hard coding a human readable string as values in a database. (What happens if the client says that "Buy" should become "Purchase"? Now the UI shows "Purchase" everywhere but you need to keep setting "Buy" in the database.)
So, if you store certain values in the database as integers, then at some point, you're going to need to show them to the user as strings, and I think the only way you can do that is programatically.
You could move this info into another object but, IMHO, I'd say this is overkill. You'd then have to add another database table. Add another 'admin' section for adding, removing and renaming these values and so on. Not to mention that if you had several columns, in different models that needed this behavior, you'd either have to create lots of these objects (ex: stock_positions, stock_actions, transaction_kinds, etc...) or you'd have to design it generically enough to use polymorphic associations. Finally, if the position name is hard coded, then you lose the ability to easy localize it at a later date.
#frankodwyer: I'd have to agree that using a helper method is probably the best way to go. I was hoping their might be a "slicker" way to do this, but it doesn't look like it. For now, I think the best method is to create a new helper module, maybe something like StringsHelper, and stuff a bunch of methods in their for converting model constants to strings. That way I can use all the I18N stuff in the helper to pull out the localized string if I need to in the future. The annoying part is that if someone needs to add a new value to the models column, then they will also have to add a check for that in the helper. Not 100% DRY, but I guess "close enough"...
Thanks to both of you for the input.
Kenny
Why not use the properties of a native data structure? example:
class Stock < ActiveRecord::Base
ACTIONS = [nil,'buy','sell']
end
Then you could grab them using Stock::ACTIONS[1] #=> 'buy' or Stock::ACTIONS[2] #=> 'sell'
or, you could use a hash {:buy => 1, :sell => 2} and access it as Stock::ACTIONS[:buy] #=> 1
you get the idea.
#Derek P. That's the implementation I first went with and while it definitely works, it sort of breaks the MVC metaphor because the model, now has view related info defined in its class. Strings in controllers are one thing, but strings in models (in my opinion) are definitely against the spirit of clean MVC.
It also doesn't really work if you want to start localizing, so while it was the method I originally used, I don't think it's the method for future development (and definitely not in an I18N world.)
Thanks for the input though.
Sincerely,
Kenny
I wrote a plugin that may help a while ago. See this. It lets you define lists and gives you nice methods ending in _str for display purposes.

Passing parameters as path variables in ruby on rails

I'm still new to ROR, so pardon the simplicity of the question...
So http://www.example.com/controller/:id displays a record in my table, with :id being a number (1,2,3 etc.).
Is there a way I can have :id in the URL be the value of a field in the displayed record? Such that I can have http://www.example.com/controller/record_field? I want to have a human-friendly reference to specific records in my table. I'm sure this must be possible. Do I change something in routes.rb?
Thanks for the help!
The cleanest way is to add a new find method in your model (or simply use the find_by_fieldname Rails gives you in your control). Then you'll have your controller use that method instead of the regular find(params[:id]) to pull your model record.
Check out Ryan B's screencast on this here. It's pretty easy, and he's a good teacher, so you shouldn't have any problems.
I use the excellent rails plugin named friendly_id.
http://github.com/norman/friendly_id/tree/master
That should sort you out nicely. It is well documented too.
Take care around fields that might have modern Greek characters—might need to figure a work around for those.
Jon Smock's solution will work, too. I tend to prefer the following.
class Hamburger << ActiveRecord::Base
#this normally defaults to id
def to_param
name
end
end
class SomeModelController << ApplicationController
def show
#hamburger = Hamburger.find(params[:id]) #still default code
end
end
#goes in some view
This is the <%= link_to "tastiest hamburger ever", url_for(#hamburger) %>.
This is, loosely speaking, an SEO technique (beautiful URLs are also user-friendly and I suggest them to absolutely everyone even if you don't care about SEO, for example on pages behind a login). I have a more extended discussion of Rails SEO, which includes other tips like this, here.
Important tip: You should consider, at design-time, what you are going to do if the param should change. For example, in my hamburger scenario, it is entirely possible that I might rename "Sinfully Delicious Cheeseburger" to "Triple Bypass". If that changes URLs, there are some possible implications, such as breakage of customer links to my website. Accordingly, for production use I usually give these models an immutable permalink attribute which I initialize to be human-meaningful exactly once. If the object later changes, oh well, the URL stays the same. (There are other solutions -- that is just the easiest one.)

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