I am wondering if it's possible to reference an object's attribute.
The object User have attribute first_name, so normally if we want to update the first name attribute we do:
user0 = User.new()
user0.update_attribute(:first_name, "joe")
now my question is can I update the :first_name attribute through another variable/symbol like so:
user0.update_attribute(:fname_ref, "jack")
user0.first_name #=> has the value jack
I was looking for variable reference like in Perl, but came up nothing in Ruby.
---------- EDIT
I am in the middle of doing the lynda ruby on rails tutorial, and in the middle of creating a module to adjust positions of items in a table.
unfortunately when I first started I named my tables columns differently
pages.page_position, subjects.subject_position, sections.section_position
now the module PositionMover is to be used accross three models, so now
I have a problem since the attributes names are different for each model
so I thought no worry I'll just create a pointer / refference for each model
:position = :pages_position , :position = :subjects_position , :position = :section_position
hence the question , if its even possible to do it.
if its not possible , any suggestion what should I do , so the module can
be used accross three different models , with different attribute names.
sorry I am a newbie.
Symbols are not like variables, they are actually a object type, like String or Fixnum so you can have a variable that is of type symbol.
I think this is what you are looking for:
attribute = :first_name
user0.update_attribute(attribute, "jack")
user0.first_name #=> has the value jack
Update: If you have a String and need to convert to a symbol, (I'm not sure if you need this for update_attribute)
foo = "string"
foo.to_sym #=> :string
Use the alias_attribute . Define into each model like :
Page model
alias_attribute :position , :pages_position
Subject Model
alias_attribute :position , :subjects_position
Section Model
alias_attribute :position , :section_position
And use (Model.position = values) with each model . Hope Its solution of your problem .
You can also use send docs and use symbols or strings to reference the attribute's methods. send can be incredibly useful since it enables you to choose the method that you'll be invoking at runtime.
Eg
user.first_name = "Jack" # set first_name to Jack
# Note: method "first_name=" (a settor) is being used
attribute = "first_name"
user.send attribute + "=", "Jack" # set first_name to Jack
# The string "first_name=" is coerced into
# a symbol
attribute = :first_name
val = user.send attribute # => returns "Jack"
see the definition of update_attribute in the ActiveRecord::Persistence module on github:
def update_attribute(name, value)
name = name.to_s
verify_readonly_attribute(name)
send("#{name}=", value)
save(:validate => false)
end
this leads me to believe you could add the following to your model to achieve that behavior:
alias_method :fname_ref= :first_name=
I'd be interested to know why you want to do that as #Andrew Marshall asked.
Related
This question is asked many times on SO. The main problem is nothing got fits into my situation.
Case is, I am not able to store typed content as array in database column.
text_field whose code is:
= text_field_tag 'product[keywords][]', #product.keywords, class: 'tab-input
product_keywords'
In controller strong parameters are:
params.require(:product).permit(:id, :name, :keywords => [])
Jquery code that is not not removing value upon deletion when typed wrong value but it add commas after each element as I want to take commas seperated value in one column.
$(document).on 'keyup', '.product_keywords', ->
keyword = #value.replace(/(\w)[\s,]+(\w?)/g, '$1, $2')
if keyword != #value
#value = keyword
return
model code:
serialize :keywords, Array
migration code:
class AddKeywordsToProducts < ActiveRecord::Migration[5.1]
def change
add_column :products, :keywords, :text
end
end
So, if someone writes, abc and hit space a comma is added in the end. after three typed words it will look like:
abc, dbx, she
now I want to store it as array in column but its not storing properly.
it stores as:
["abc, dbx, she"]
Also please can anybody tell me the best cases to handle these cases?
Plus best practices to deal with such cases using ruby so I will learn it for future?
You probably want a custom serializer as shown here. So instead of:
serialize :keywords, Array
You might do somewhat like:
serialize :keywords, KeywordSerializer
And somewhere in helpers:
class KeywordSerializer
def self.dump(what)
what.join(", ")
end
def self.load(what)
what.split(/\s*,\s*/)
end
end
Passing array elements using single form tag is not possible to pass as a array and passing array as a string, you need to process it near white-listing your params,
permitted_params = params.require(:product).permit(:id, :name, :keywords => [])
permitted_params[:keywords] = permitted_params[:keywords][0].split(/\s*,\s*/)
I’m using Rails 4.2.7. I have an attribute in my model that doesn’t have a database field underneath it
attr_accessor :division
This gets initialized when I create a new object.
my_object = MyObject.new(:name => name,
:age => get_age(data_hash),
:overall_rank => overall_rank,
:city => city,
:state => state,
:country => country,
:age_group_rank => age_group_rank,
:gender_rank => gender_rank,
:division => division)
What I would like is when this field gets set (if it is not nil), for two other fields that do have mappings in the database to get set. The other fields would be substrings of the “division” field. Where do I put that logic?
I'd probably drop the attr_accessor :division and do it by hand with:
def division=(d)
# Break up `d` as needed and assign the parts to the
# desired real attributes.
end
def division
# Combine the broken out attributes as needed and
# return the combined string.
end
With those two methods in place, the following will all call division=:
MyObject.new(:division => '...')
MyObject.create(:division => '...')
o = MyObject.find(...); o.update(:division => '...')
o = MyObject.find(...); o.division = '...'
so the division and the broken out attributes will always agree with each other.
If you try to use one of the lifecycle hooks (such as after_initialize) then things can get out of sync. Suppose division has the form 'a.b' and the broken out attributes are a and b and suppose that you're using one of the ActiveRecord hooks to break up division. Then saying:
o.division = 'x.y'
should give you o.a == 'x' but it won't because the hook won't have executed yet. Similarly, if you start with o.division == 'a.b' then
o.a = 'x'
won't give you o.division == 'x.b' so the attributes will have fallen out of sync again.
I see couple of options here
You can add it in your controller as follows
def create
if params[:example][:division]
# Set those params here
end
end
Or you can use before_save In your model
before_save :do_something
def do_something
if division
# Here!
end
end
I'm having a problem overcoming the new strong params requirement in Rails 4 using Hstore and dynamic accessors
I have an Hstore column called :content which I want to use to store content in multiple languages, ie :en, :fr, etc. And I don't know which language upfront to set them in either the model or the controller.
store_accessor :content, [:en, :fr] #+226 random other il8n languages won't work.
How can I override strong params (or allow for dynamic hstore keys) in rails 4 for one column?
params.require(:article).permit(
:name, :content,
:en, :fr #+226 random translations
)
Short of...
params.require(:article).permit!
which of course does work.
If I understand correctly, you would like to whitelist a hash of dynamic keys. You can use some ruby code as follows to do this:
params.require(:article).permit(:name).tap do |whitelisted|
whitelisted[:content] = params[:article][:content]
end
This worked for me, hope it helps!
I'm doing something similar and found this to be a bit cleaner and work well.
Assuming a model called Article you can access your :content indexed stored_attributes like this: Article.stored_attributes[:content]
So your strong params looks like this:
params.require(:article).permit(:name, content: Article.stored_attributes[:content])
Assuming your params are structured like: { article => { name : "", content : [en, fr,..] } }
As people have said, it is not enough to permit the :content param - you need to permit the keys in the hash as well. Keeping things in the policy, I did that like so:
# in controller...
def model_params
params.permit(*#policy.permitted_params(params))
end
# in policy...
def permitted_params(in_params = {})
params = []
params << :foo
params << :bar
# ghetto hack support to get permitted params to handle hashes with keys or without
if in_params.has_key?(:content)
content = in_params[:content]
params << { :content => content.empty? ? {} : content.keys }
end
end
I'm facing a weird behavior in Rails 3 model instantiation.
So, I have a simple model :
class MyModel < ActiveRecord::Base
validates_format_of :val, :with => /^\d+$/, :message => 'Must be an integer value.'
end
Then a simple controller :
def create
#mod = MyModel.new(params[:my_model])
if #mod.save
...
end
end
first, params[:my_model].inspect returns :
{:val => 'coucou :)'}
But after calling #mod = MyModel.new(params[:my_model]) ...
Now, if I call #mod.val.inspect I will get :
0
Why am I not getting the original string ?
At the end the validates succeed because val is indeed an integer.
Is this because val is defined as an integer in the database ?
How do I avoid this behavior and let the validation do his job ?
If val is defined as an integer in your schema then calling #my_model.val will always return an integer because AR does typecasting. That's not new to rails 3, it's always worked that way. If you want the original string value assigned in the controller, try #my_model.val_before_type_cast. Note that validates_format_of performs its validation on this pre-typecast value, so you don't need to specify that there.
EDIT
Sorry I was wrong about the "performs its validation on this pre-typecast value" part. Looking at the code of the validation, it calls .to_s on the post-typecast value which in your case returns "0" and therefore passes validation.
I'd suggest not bothering with this validation to be honest. If 0 is not a valid value for this column then validate that directly, otherwise just rely on the typecasting. If the user enters 123 foo you'll end up with 123 in the database which is usually just fine.
There is also better fitting validator for your case:
http://guides.rubyonrails.org/active_record_validations_callbacks.html#validates_numericality_of
I'm fairly new to rails, working on a Rails 3 app with a Profile model for users.
In the profile Model I'd like to have a "name" entry, and I'd like to be able to access logical variations of it using simple syntax like:
user.profile.name = "John Doe"
user.profile.name.first = "John"
user.profile.name.last = "Doe"
Is this possible, or do I need to stick with "first_name" and "last_name" as my fields in this model?
It's possible, but I wouldn't recommend it.
I would just stick with first_name and last_name if I were you and add a method fullname:
def fullname
"#{first_name} #{last_name}"
end
Edit:
If you really do want user.profile.name, you could create a Name model like this:
class Name < ActiveRecord::Base
belongs_to :profile
def to_s
"#{first} #{last}"
end
end
This allows you to do:
user.profile.name.to_s # John Doe
user.profile.name.first # John
user.profile.name.last # Doe
The other answers are all correct, in so far as they ignore the #composed_of aggregator:
class Name
attr_reader :first, :last
def initialize(first_name, last_name)
#first, #last = first_name, last_name
end
def full_name
[#first, #last].reject(&:blank?).join(" ")
end
def to_s
full_name
end
end
class Profile < ActiveRecord::Base
composed_of :name, :mapping => %w(first_name last_name)
end
# Rails console prompt
> profile = Profile.new(:name => Name.new("Francois", "Beausoleil"))
> profile.save!
> profile = Profile.find_by_first_name("Francois")
> profile.name.first
"Francois"
As noted on the #composed_of page, you must assign a new instance of the aggregator: you cannot just replace values within the aggregator. The aggregator class acts as a Value, just like a simple string or number.
I also sent a response yesterday with a very similar answer: How best to associate an Address to multiple models in rails?
As Capt. Tokyo said that's a horrible idea but here's how you would do it:
rails g model User full_name:hash
Then you would store data in it like so:
user = User.new
user.full_name = {:first => "Forrest", :last => "Gump"}
Now your problems begin.
To search the field requires both names and you can't do a partial search like searching for all people with the same last name. Worst of all you can store anything in the field! So imagine another programmer mistypes one of the field names so for a week you have {:fist => "Name", :last => "Last"} being inserted into the database! Noooooooooooooooooo!
If you used proper field names you could do this:
user = User.new(:first_name => "First", :last_name => "Last")
Easy to read and no need for hashes. Now that you know how to do it the wrong way, do it the right way. :)
FYI (assume you have a field fullname. ie your profile.name = "John Doe")
class Profile
def name
#splited_name ||= fullname.split # #splited_name would cache the result so that no need to split the fullname every time
end
end
Now, you could do something like this:
user.profile.fullname # "John Doe"
user.profile.name.first # "John"
user.profile.name.last # "Doe"
Note the following case:
user.profile.fullname = "John Ronald Doe"
user.profile.name.first # "John"
user.profile.name.second # "Ronald"
user.profile.name.last # "Doe"
I agree with captaintokyo. You won't miss out the middle names.
Also this method assume no Chinese, Japanese names are input. It's because those names contain no spaces in between first name and last name normally.