Here's the model:
class Target
include DataMapper::Resource
property :id, Serial
property :owed, Integer, :default => 0, :required => true
property :served, Integer, :default => 0, :required => true
def go
#owed -= 1
#served += 1
save
end
end
When I do this:
t = Target.first
t.go
It doesn't seem to update the database. Any ideas?
The resource isn't saving because DataMapper doesn't know that the owed and served properties have been changed. #save will only save the resource, if the resource is considered dirty by DataMapper.
Instead, change the values of self.owed and self.served, which will cause a state change within the resource, which will mark the resource as dirty and allow #save to trigger. Additionally, you can simplify the go method using #update:
def go
update(:owed => self.owed - 1, :served => self.served + 1)
end
You need to use self.owed and self.served instead:
def go
self.owed -= 1
self.served += 1
save
end
Related
I have a model
class Transaction < ActiveRecord::Base
end
I have a transaction_type column which is an integer.
How can I create an enumeration that I could map values to names like:
one_time = 1
monthly = 2
annually = 3
So in the db column, the values would be 1, 2 or 3.
Also, whenever I create a new instance, or save a model and the field wasn't set like:
#transaction = Transaction.new(params)
It should default to 1 (on_time).
I'm not sure how I can do this?
basically the same answer as Amit, slight variation
class TransactionType
TYPES = {
:one_time => 1,
:monthly => 2,
:annually => 3
}
# use to bind to select helpers in UI as needed
def self.options
TYPES.map { |item| [item[0], item[1].to_s.titleize] }
end
def self.default
TYPES[:one_time]
end
end
one way to control the default value
class Transaction < ActiveRecord::Base
before_create :set_default_for_type
def set_default_for_type
type = TransactionType.default unless type.present?
end
end
but - best way is to just apply the defaults on your database column and let ActiveRecord get it from there automatically
NOTE: it might also make sense to just have a TransactionType ActiveRecord object instead of above, depends on your situation, i.e.
# on Transaction with type_id:integer
belongs_to :type, class_name: "TransactionType"
You can map the values by creating a constant either in the same Transaction model or by creating a new module and place it inside that as explained by #KepaniHaole
In Transaction model, you can do it like :
class Transaction < ActiveRecord::Base
TRANSACTION_TYPES = { 'one_time' => 1, 'monthly' => 2, 'monthly' => 3 }
end
You can access these values by accessing the constant as
Transaction::TRANSACTION_TYPES['one_time'] # => 1
Transaction::TRANSACTION_TYPES['monthly'] # => 2
Transaction::TRANSACTION_TYPES['monthly'] # => 3
To add a default value to transaction_type column just create a new migration with :
def up
change_column :transactions, :transaction_type, :default => Transaction::TRANSACTION_TYPES['one_time']
end
With this, every time you create a Transaction object without passing transaction_type, the default value 1 with be stored in it.
Maybe you could try something like this? Ruby doesn't really support c-style enums..
module TransactionType
ONCE = 1
MONTHLY = 2
ANUALLY = 3
end
then you could access their values like so:
#transaction = Transaction.new(TransactionType::ONCE)
I have a situation where an attribute can be created through a JSON API. But once it is created, I want to prevent it from ever being updated.
This constraint causes my first solution, which is using attr_accessible, to be insufficient. Is there a nice way to handle this type of situation in rails, or do I have to perform a manual check in the update method?
You can use attr_readonly, this will allow the value to be set on creation, but ignored on update.
Example:
class User < ActiveRecord::Base
attr_accessible :name
attr_readonly :name
end
> User.create(name: "lorem")
> u = User.first
=> #<User id: 1, name: "lorem">
> u.name = "ipsum"
=> "ipsum"
> u.save
=> true
> User.first.name
=> "lorem"
There is not a nice way to do that as far as I know, you have to write a custom filter
before_update :prevent_attributes_update
def prevent_attribute_updates
%w(attr1, attr2).each do |a|
send("#{attr1}=", send("#{attr1}_was")) unless self.send("#{attr1}_was").blank?
end
end
When I execute a Model.create method, if I specify a value for :id, it later gets nullified. Example:
Model.create (
:id => 50,
:name => Joe,
:enabled => yes
)
Instead what I have to do is use a .new and store it in a class variable, store my id value via the class variable, and then finally call a save:
m = Model.new (
:name => Joe,
:enabled => yes
)
m.id = 50
m.save
I am trying to execute this code in a seeds.rb, and this is NOT very DRY code. How can I do this better and achieve the same results?
id is just attr_protected. To prevent that, you can override the list of default protected attributes. Be careful doing this anywhere that attribute information can come from the outside. The id field is default protected for a reason.
class Model < ActiveRecord::Base
private
def attributes_protected_by_default
[]
end
end
or go with #Leo answer
This might be an answer for you. Model.create is basically a Model.new followed by a Model.save and since you are changing the id and saving again you might as well do
m = Model.new {
:name => Joe,
:enabled => yes
}
m.id = 50
m.save!
That will rid you of doing two saves.
I have a class Sample
Sample.class returns
(id :integer, name :String, date :date)
and A hash has all the given attributes as its keys.
Then how can I initialize a variable of Sample without assigning each attribute independently.
Something like
Sample x = Sample.new
x.(attr) = Hash[attr]
How can I iterate through the attributes, the problem is Hash contains keys which are not part of the class attributes too
class Sample
attr_accessor :id, :name, :date
end
h = {:id => 1, :name => 'foo', :date => 'today', :extra1 => '', :extra2 => ''}
init_hash = h.select{|k,v| Sample.method_defined? "#{k}=" }
# This will work
s = Sample.new
init_hash.each{|k,v| s.send("#{k}=", v)}
# This may work if constructor takes a hash of attributes
s = Sample.new(init_hash)
Take a look at this article on Object initialization. You want an initialize method.
EDIT You might also take a look at this SO post on setting instance variables, which I think is exactly what you're trying to do.
Try this:
class A
attr_accessor :x, :y, :z
end
a = A.new
my_hash = {:x => 1, :y => 2, :z => 3, :nono => 5}
If you do not have the list of attributes that can be assigned from the hash, you can do this:
my_attributes = (a.methods & my_hash.keys)
Use a.instance_variable_set(:#x = 1) syntax to assign values:
my_attributes.each do |attr|
a.instance_variable_set("##{attr.to_s}".to_sym, my_hash[attr])
end
Note(Thanks to Abe): This assumes that either all attributes to be updated have getters and setters, or that any attribute which has getter only, does not have a key in my_hash.
Good luck!
I'm building an application where users can purchase tracking numbers. I have an Order model and an Order Transaction model. If the Order Transaction returns from the gateway with success, I'm using an after_save callback to trigger a method that creates the tracking numbers and inserts them into the database. Sometimes a user just orders one, but if they order more than one, I can't seem to get rails to create and insert more than one record.
Here's what I'm using -- I've never had to user a loop like this, so I'm not sure what I'm doing wrong.
def create_trackables
if self.success == true
#order = Order.find(order_id)
#start = 0
while #start < #order.total_tokens
#trackable_token = Tracker.create_trackable_token
#start += 1
#trackable ||= Tracker.new(
:user_id => #current_user,
:token => #trackable_token,
:order_id => order_id
)
#trackable.save
end
end
end
dmarkow is right that you should use trackable instead of #trackable but you also should be using = instead of ||=. You also might as well just use create. Here's how I'd write it: def create_trackables
return unless self.success
order = Order.find(order_id) #you shouldn't need this line if it has_one :order
1.upto(order.total_tokens) do
Tracker.create!(
:user_id => #current_user,
:token => Tracker.create_trackable_token,
:order_id => order_id
)
end
end
Change #trackable to trackable to keep it scoped to the loop. Otherwise, the second time the loop runs, #trackable already has a value so the call to Tracker.new doesn't execute, and the #trackable.save line just keeps re-saving the same record. (Edit: Also remove the ||= and just use =).
def create_trackables
if self.success == true
#order = Order.find(order_id)
#start = 0
while #start < #order.total_tokens
#trackable_token = Tracker.create_trackable_token
#start += 1
trackable = Tracker.new(
:user_id => #current_user,
:token => #trackable_token,
:order_id => order_id
)
trackable.save
end
end
end