In Rails, I have a class name User, in which I just want to look at :name, :address, :age
I would like to write a piece of code that's something like:
user = User.new
[name, address, age].zip(["Name", "Address", 10]).each do |attribute, val|
user.attribute = val
end
The thing is I don't know how to do it properly, since user.attribute is obviously not a valid line. In other word, is there anyway so that user.attribute gets evaluated as user.name, user.address, user.age depends on the loop?
You should use send method
user.send "#{attribute}=", val
If attribute is, say, :name, then the line above is equivalent to
user.name = val
Actually I can do it this way:
[name, address, age].zip(["Name", "Address", 10]).each do |attribute, val|
user[attribute] = val
end
This way works, too
user.send(:name) would be the same as calling user.name, so you may want to try that.
user = User.new
[name, address, age].zip(["Name", "Address", 10]).each do |attribute, val|
user.write_attribute(attribute, val)
end
But that's what I'd write:
user = User.new
user.attributes = {name => "Name", address => "Address", age => 10}
Related
I have a table A(:name, :address, :phone) and want to update the names and addresses of all the records. The following lines of code helps me doing it but takes a lot of time :
A.find_each(batch_size: 10000) do |a|
new_name = "xyz"
new_address = "abc"
A.find(a.id).update(name: name, address: new_address)
end
It takes times because of the last line as I am finding the record first, then updating it. Now when I do this :
A.find_each(batch_size: 10000) do |a|
a.name = "xyz"
a.address = "abc"
a.save
end
The names and addresses don't get updated in this case but a.save returns true. What could be wrong?
Can you try printing out the errors while saving if any:
A.find_each(batch_size: 10000) do |a|
a.name = "xyz"
a.address = "abc"
a.save
puts a.errors.full_messages
end
Try to do this like:
A.find_each(batch_size: 10000){ |a| a.update_attributes(name: 'name', address: 'address', phone: 23213) }
If you want all records to be updated with same value, the below solution will be fast.
A.update_all(name: 'xyz', address: 'abc')
You can fire direct SQL query and update directly using single SQL statement
A.find_by_sql "UPDATE table SET name = 'abc' and address = 'xyz'";
A.update_all(name: 'xyz', address: 'abc')
I have a Rails 3 app which JSON encodes objects in order to store them in a Redis key/value store.
When I retrieve the objects, I'm trying to decode the JSON and instantiate them from the data like so:
def decode(json)
self.new(ActiveSupport::JSON.decode(json)["#{self.name.downcase}"])
end
The problem is that doing this involves mass assignment which is disallowed (for good reason I'm told!) for attributes I haven't given attr_writer ability to.
Is there a way I can bypass the mass assignment protection just for this operation only?
assign_attributes with without_protection: true seems less intrusive:
user = User.new
user.assign_attributes({ :name => 'Josh', :is_admin => true }, :without_protection => true)
user.name # => "Josh"
user.is_admin? # => true
#tovodeverett mentioned in the comment you can also use it with new, like this in 1 line
user = User.new({ :name => 'Josh', :is_admin => true }, :without_protection => true)
EDIT: kizzx2's Answer is a much better solution.
Kind of a hack, but...
self.new do |n|
n.send "attributes=", JSON.decode( json )["#{self.name.downcase}"], false
end
This invokes attributes= passing false for the guard_protected_attributes parameter which will skip any mass assignment checks.
You can create a user also in this way which is not doing the mass assignment.
User.create do |user|
user.name = "Josh"
end
You may want to put this into a method.
new_user(name)
User.create do |user|
user.name = name
end
end
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.
I'm answering my own questions - just putting this up here for google-fu in case it helps someone else. This code allows you to validate the presence of one field in a list. See comments in code for usage. Just paste this into lib/custom_validations.rb and add require 'custom_validations' to your environment.rb
#good post on how to do stuff like this http://www.marklunds.com/articles/one/312
module ActiveRecord
module Validations
module ClassMethods
# Use to check for this, that or those was entered... example:
# :validates_presence_of_at_least_one_field :last_name, :company_name - would require either last_name or company_name to be filled in
# also works with arrays
# :validates_presence_of_at_least_one_field :email, [:name, :address, :city, :state] - would require email or a mailing type address
def validates_presence_of_at_least_one_field(*attr_names)
msg = attr_names.collect {|a| a.is_a?(Array) ? " ( #{a.join(", ")} ) " : a.to_s}.join(", ") +
"can't all be blank. At least one field (set) must be filled in."
configuration = {
:on => :save,
:message => msg }
configuration.update(attr_names.extract_options!)
send(validation_method(configuration[:on]), configuration) do |record|
found = false
attr_names.each do |a|
a = [a] unless a.is_a?(Array)
found = true
a.each do |attr|
value = record.respond_to?(attr.to_s) ? record.send(attr.to_s) : record[attr.to_s]
found = !value.blank?
end
break if found
end
record.errors.add_to_base(configuration[:message]) unless found
end
end
end
end
end
This works for me in Rails 3, although I'm only validating whether one or the other field is present:
validates :last_name, :presence => {unless => Proc.new { |a| a.company_name.present? }, :message => "You must enter a last name, company name, or both"}
That will only validate presence of last_name if company name is blank. You only need the one because both will be blank in the error condition, so to have a validator on company_name as well is redundant. The only annoying thing is that it spits out the column name before the message, and I used the answer from this question regarding Humanized Attributes to get around it (just setting the last_name humanized attribute to ""
I have an object now:
class Items
attr_accessor :item_id, :name, :description, :rating
def initialize(options = {})
options.each {
|k,v|
self.send( "#{k.to_s}=".intern, v)
}
end
end
I have it being assigned as individual objects into an array...
#result = []
some loop>>
#result << Items.new(options[:name] => 'name', options[:description] => 'blah')
end loop>>
But instead of assigning my singular object to an array... how could I make the object itself a collection?
Basically want to have the object in such a way so that I can define methods such as
def self.names
#items.each do |item|
item.name
end
end
I hope that makes sense, possibly I am overlooking some grand scheme that would make my life infinitely easier in 2 lines.
A few observations before I post an example of how to rework that.
Giving a class a plural name can lead to a lot of semantic issues when declaring new objects, as in this case you'd call Items.new, implying you're creating several items when in fact actually making one. Use the singular form for individual entities.
Be careful when calling arbitrary methods, as you'll throw an exception on any misses. Either check you can call them first, or rescue from the inevitable disaster where applicable.
One way to approach your problem is to make a custom collection class specifically for Item objects where it can give you the information you need on names and such. For example:
class Item
attr_accessor :item_id, :name, :description, :rating
def initialize(options = { })
options.each do |k,v|
method = :"#{k}="
# Check that the method call is valid before making it
if (respond_to?(method))
self.send(method, v)
else
# If not, produce a meaningful error
raise "Unknown attribute #{k}"
end
end
end
end
class ItemsCollection < Array
# This collection does everything an Array does, plus
# you can add utility methods like names.
def names
collect do |i|
i.name
end
end
end
# Example
# Create a custom collection
items = ItemsCollection.new
# Build a few basic examples
[
{
:item_id => 1,
:name => 'Fastball',
:description => 'Faster than a slowball',
:rating => 2
},
{
:item_id => 2,
:name => 'Jack of Nines',
:description => 'Hypothetical playing card',
:rating => 3
},
{
:item_id => 3,
:name => 'Ruby Book',
:description => 'A book made entirely of precious gems',
:rating => 1
}
].each do |example|
items << Item.new(example)
end
puts items.names.join(', ')
# => Fastball, Jack of Nines, Ruby Book
Do you know the Ruby key word yield?
I'm not quite sure what exactly you want to do. I have two interpretations of your intentions, so I give an example that makes two completely different things, one of them hopefully answering your question:
class Items
#items = []
class << self
attr_accessor :items
end
attr_accessor :name, :description
def self.each(&args)
#items.each(&args)
end
def initialize(name, description)
#name, #description = name, description
Items.items << self
end
def each(&block)
yield name
yield description
end
end
a = Items.new('mug', 'a big cup')
b = Items.new('cup', 'a small mug')
Items.each {|x| puts x.name}
puts
a.each {|x| puts x}
This outputs
mug
cup
mug
a big cup
Did you ask for something like Items.each or a.each or for something completely different?
Answering just the additional question you asked in your comment to tadman's solution: If you replace in tadman's code the definition of the method names in the class ItemsCollection by
def method_missing(symbol_s, *arguments)
symbol, s = symbol_s.to_s[0..-2], symbol_s.to_s[-1..-1]
if s == 's' and arguments.empty?
select do |i|
i.respond_to?(symbol) && i.instance_variables.include?("##{symbol}")
end.map {|i| i.send(symbol)}
else
super
end
end
For his example data you will get following outputs:
puts items.names.join(', ')
# => Fastball, Jack of Nines, Ruby Book
puts items.descriptions.join(', ')
# => Faster than a slowball, Hypothetical playing card, A book made entirely of precious gems
As I don't know about any way to check if a method name comes from an attribute or from another method (except you redefine attr_accessor, attr, etc in the class Module) I added some sanity checks: I test if the corresponding method and an instance variable of this name exist. As the class ItemsCollection does not enforce that only objects of class Item are added, I select only the elements fulfilling both checks. You can also remove the select and put the test into the map and return nil if the checks fail.
The key is the return value. If not 'return' statement is given, the result of the last statement is returned. You last statement returns a Hash.
Add 'return self' as the last line of initialize and you're golden.
Class Item
def initialize(options = {})
## Do all kinds of stuff.
return self
end
end