I have a Reservation model that takes an appointment attribute as date and has a virtual attribute duration that indicates how long the appointment will take. The real attribute, booking_end takes a Time that is referenced all over my application. However, for ease of input, we use duration instead of choosing another Time. The fields are below:
def duration
( (booking_end - date) / 1.hour ).round( 2 ) rescue nil
end
def duration=(temp)
if ( true if Float(temp) rescue false )
self.booking_end = time_round(date + temp.to_f.hours, 15.minutes)
else
errors.add(:duration, "must be a number, stated in hours.")
self.booking_end = nil
end
end
The whole thing fails when I reference the date field while creating a new record. I get a 'nil' error because date hasn't been initialized. How can I fix this problem? The rest of this works when updating existing records.
When you call Reservation.new(:date => date, :duration => duration) ActiveRecord::Base assigns attributes values this way (see assign_attributes method):
attributes.each do |k, v|
...
respond_to?("#{k}=") ? send("#{k}="", v)
...
Hash#each method iterates through the values the way that :duration key is accessed before :date one, so date is nil inside the duration= method:
ruby-1.8.7-p302 > {:date => Date.today, :duration => 5}.each do |key,value|
ruby-1.8.7-p302 > puts "#{key} = #{value}"
ruby-1.8.7-p302 ?> end
duration = 5
date = 2010-11-17
So you'll have to call duration= after initialization.
Or you can redefine Reservation#initialize to call super with :date and then update_attributes with the rest of parameters.
I tried to initialize the model with
Reservation.new(params[:reservation][:date])
and then call update_attributes on it. This works in console, but not otherwise. The only workaround that seems to take hold is stripping duration out of the params hash and then passing it back before save. This seems really stupid, though, and probably not the right or Rails way to do things. Using 4 lines where one should suffice.
duration = params[:reservation][:duration]
params[:reservation].delete('duration')
#reservation = Reservation.new(params[:reservation])
#reservation.duration = duration
# Then go to save, etc.
Is there a different way to initialize the model or perhaps access the attributes hash from inside the model?
Related
Using select_date gives me back a params[:my_date] with year, month and day attributes. How do get a Date object easily? I'm hoping for something like params[:my_date].to_date.
I'm happy to use date_select instead as well.
Using date_select gives you 3 separate key/value pairs for the day, month, and year respectively. So you can pass them into Date.new as parameters to create a new Date object.
An example date_select returned params for an Event model:
"event"=>
{"name"=>"Birthday",
"date(1i)"=>"2012",
"date(2i)"=>"11",
"date(3i)"=>"28"},
Then to create the new Date object:
event = params[:event]
date = Date.new event["date(1i)"].to_i, event["date(2i)"].to_i, event["date(3i)"].to_i
You may instead decide to wrap this logic in a method:
def flatten_date_array hash
%w(1 2 3).map { |e| hash["date(#{e}i)"].to_i }
end
And then call it as date = Date.new *flatten_date_array params[:event]. But this is not logic that truly belongs in a controller, so you may decide to move it elsewhere. You could even extend this onto the Date class, and call it as date = Date.new_from_hash params[:event].
Here is another one:
# view
<%= date_select('event', 'date') %>
# controller
date = Date.civil(*params[:event].sort.map(&:last).map(&:to_i))
Found at http://kevinlochner.com/use-rails-dateselect-without-an-activerecord
I use the following method, which has the following benefits:
it doesn't have to explicitly name param keys xxx(1i) through xxx(3i) (and thus could be modified to capture hour and minute simply by changing Date to DateTime); and
it extracts a date from a set of params even when those params are populated with many other key-value pairs.
params is a hash of the format { xxx(1i): '2017', xxx(2i): 12, xxx(3i): 31, ... }; date_key is the common substring xxx of the target date parameters.
def date_from_params(params, date_key)
date_keys = params.keys.select { |k| k.to_s.match?(date_key.to_s) }.sort
date_array = params.values_at(*date_keys).map(&:to_i)
Date.civil(*date_array)
end
I chose to place this as a class method of ApplicationRecord, rather than as an instance helper method of ApplicationController. My reasoning is that similar logic exists within the ActiveRecord instantiator (i.e., Model.new) to parse dates passed in from Rails forms.
Here is the another one
Date.civil(params[:event]["date(1i)"].to_i,params[:event]["date(2i)"].to_i,params[:event]["date(3i)"].to_i)
Here is another one for rails 5:
module Convert
extend ActiveSupport::Concern
included do
before_action :convert_date
end
protected
def convert_date
self.params = ActionController::Parameters.new(build_date(params.to_unsafe_h))
end
def build_date(params)
return params.map{|e| build_date(e)} if params.is_a? Array
return params unless params.is_a? Hash
params.reduce({}) do |hash, (key, value)|
if result = (/(.*)\(\di\)\z/).match(key)
params_name = result[1]
date_params = (1..3).map do |index|
params.delete("#{params_name}(#{index}i)").to_i
end
hash[params_name] = Date.civil(*date_params)
else
hash[key] = build_date(value)
end
hash
end
end
end
You need to include it to your controller or application_controller.rb:
class ApplicationController < ActionController::Base
include Convert
end
With the date_select example #joofsh's answer, here's a "one liner" I use, presuming the date field is called start_date:
ev_params = params[:event]
date = Time.zone.local(*ev_params.select {|k,v| k.to_s.index('start_date(') == 0 }.sort.map {|p| p[1].to_i})
Rails 5 + use select_date, in your view note the prefix
<%= select_date Date.today - 3.months, prefix: :start_date %>
then in your controller you simply process:
your_date = Date.civil(params[:start_date][:year].to_i, params[:start_date][:month].to_i, params[:start_date][:day].to_i)
the prefix binds the three date components into a single object.
Or simply do this:
your_date_var = Time.parse(params[:my_date])
I want to implement a method that checks if a model's instance has only nil or empty attributes, except from its id or timestamps.
I've made use of an auxiliary method that removes a key from Hash and return the remaining hash ( question 6227600)
class ActiveRecord::Base
def blank?
self.attributes.remove("id","created_at","updated_at").reject{|attr| self[attr].blank?}.empty?
end
end
I guess that there may be much simpler, efficient or safer way to do this. Any suggestion?
def blank?
self.attributes.all?{|k,v| v.blank? || %w(id created_at updated_at).include?(k)}
end
My response is almost the same that tadman gave, but expressed in a more concise way.
Be careful with two situations:
- **blank?** is not a good choice as name, since if you call **object_a.object_b.blank?** trying to know if there is or not a object_b inside object_a, you'll get true event if the object exists. **empty?** seems a better name
- If databases sets defaults values, it can be tricky.
EDIT: Since build an array every iteration is slow (thanks tadman), a beter solution is:
def empty?
ignored_attrs = {'id' => 1, 'created_at' => 1, 'updated_at' => 1}
self.attributes.all?{|k,v| v.blank? || ignored_attrs[k]}
end
You could just check that all the properties in the attributes hash are not present, or the converse:
class ActiveRecord::Base
def blank?
!self.attributes.find do |key, value|
case (key)
when 'id', 'created_at', 'updated_at'
false
else
value.present?
end
end
end
end
Unfortunately this will not account for things that are set with a default in your database, if any relationship keys are assigned, among other things. You will have to add those as exceptions, or compare the values to a known default state of some sort.
This sort of thing is probably best implemented on a case by case basis.
I am trying to use a time_select to input a time into a model that will then perform some calculations.
the time_select helper prepares the params that is return so that it can be used in a multi-parameter assignment to an Active Record object.
Something like the following
Parameters: {"commit"=>"Calculate", "authenticity_token"=>"eQ/wixLHfrboPd/Ol5IkhQ4lENpt9vc4j0PcIw0Iy/M=", "calculator"=>{"time(2i)"=>"6", "time(3i)"=>"10", "time(4i)"=>"17", "time(5i)"=>"15", "time(1i)"=>"2009"}}
My question is, what is the best way to use this format in a non-active record model. Also on a side note. What is the meaning of the (5i), (4i) etc.? (Other than the obvious reason to distinguish the different time values, basically why it was named this way)
Thank you
You can create a method in the non active record model as follows
# This will return a Time object from provided hash
def parse_calculator_time(hash)
Time.parse("#{hash['time1i']}-#{hash['time2i']}-#{hash['time3i']} #{hash['time4i']}:#{hash['time5i']}")
end
You can then call the method from the controller action as follows
time_object = YourModel.parse_calculator_time(params[:calculator])
It may not be the best solution, but it is simple to use.
Cheers :)
The letter after the number stands for the type to which you wish it to be cast. In this case, integer. It could also be f for float or s for string.
I just did this myself and the easiest way that I could find was to basically copy/paste the Rails code into my base module (or abstract object).
I copied the following functions verbatim from ActiveRecord::Base
assign_multiparameter_attributes(pairs)
extract_callstack_for_multiparameter_attributes(pairs)
type_cast_attribute_value(multiparameter_name, value)
find_parameter_position(multiparameter_name)
I also have the following methods which call/use them:
def setup_parameters(params = {})
new_params = {}
multi_parameter_attributes = []
params.each do |k,v|
if k.to_s.include?("(")
multi_parameter_attributes << [ k.to_s, v ]
else
new_params[k.to_s] = v
end
end
new_params.merge(assign_multiparameter_attributes(multi_parameter_attributes))
end
# Very simplified version of the ActiveRecord::Base method that handles only dates/times
def execute_callstack_for_multiparameter_attributes(callstack)
attributes = {}
callstack.each do |name, values|
if values.empty?
send(name + '=', nil)
else
value = case values.size
when 2 then t = Time.new; Time.local(t.year, t.month, t.day, values[0], values[min], 0, 0)
when 5 then t = Time.time_with_datetime_fallback(:local, *values)
when 3 then Date.new(*values)
else nil
end
attributes[name.to_s] = value
end
end
attributes
end
If you find a better solution, please let me know :-)
I'm trying to remove the commas from a field in a model. I want the user to type a number, i.e. 10,000 and that number should be stored in the database as 10000. I was hoping that I could do some model-side normalization to remove the comma. I don't want to depend on the view or controller to properly format my data.
I tried:
before_validation :normalize
def normalize
self['thenumber'] = self['thenumber'].to_s.gsub(',','')
end
no worky.
http://github.com/mdeering/attribute_normalizer looks like a promising solution to this common problem. Here are a few examples from the home page:
# By default it will strip leading and trailing whitespace
# and set to nil if blank.
normalize_attributes :author, :publisher
# Using one of our predefined normalizers.
normalize_attribute :price, :with => :currency
# You can also define your normalization block inline.
normalize_attribute :title do |value|
value.is_a?(String) ? value.titleize.strip : value
end
So in your case you might do something like this:
normalize_attribute :title do |value|
value.to_s.gsub(',', '')
end
I think you're doing it right. This test passes:
test "should remove commas from thenumber" do
f = Foo.new(:thenumber => "10,000")
f.save
f = Foo.find(f.id)
assert f.thenumber == "10000"
end
And I used your code.
class Foo < ActiveRecord::Base
before_validation :normalize
def normalize
self['thenumber'] = self['thenumber'].to_s.gsub(',','')
end
end
Now, my schema is set up for thenumber to be a string though, not an integer.
Started
.
Finished in 0.049666 seconds.
1 tests, 1 assertions, 0 failures, 0 errors
If you wanted to store this in the db as an integer, then you definitely need to override the setter:
def thenumber=(value)
self['thenumber'] = value.to_s.gsub(',','').to_i
end
If you do it your way, with an integer column, it gets truncated by AR....
>> f.thenumber = "10,000"
=> "10,000"
>> f.thenumber
=> 10
That's a little-known thing with Ruby and integers... it auto-casts by truncating anything that's no longer an integer.
irb(main):004:0> i = "155-brian-hogan".to_i
=> 155
Can be cool for things like
/users/155-brian-hogan
#user = User.find_by_id(params[:id])
But not so cool for what you're doing.
So either change the col to a string and use the filter, or change the setter :)
Good luck!
The problem with doing it that way is that for a while, the non-normalized stuff will exist in the object; if you have code that works on the attributes before stuff gets normalised, then that will be a problem.
You could define a setter:
def thenumber=(value)
# normalise stuff here, call write_attribute
end
Unfortunately I think a lot of the Rails form stuff writes the attributes directly, which is one of the reasons I don't tend to use it.
Or you could normalise the params in the controller before you pass them through.
Does ruby let you interchange between a . and [''] ?
I don't know, I'll try later, but I think you are supposed to use .
self.thenumber = self.thenumber.to_s.gsub(',','')
You should return true from your before_validation method, otherwise if the expression being assigned to self['thenumber'] ends up being nil or false, the data will not be saved, per the Rails documention:
If a before_* callback returns false,
all the later callbacks and the
associated action are cancelled.
Ostensibly, you are trying to normalize here then check the result of the normalization with your Rails validations, which will decide if nil/false/blank are okay or not.
before_validation :normalize
def normalize
self['thenumber'] = self['thenumber'].to_s.gsub(',','')
return true
end
I want to define a class method that has access to a local variable. So this would be different for each instance of the class. I know you can make a class method dynamic with lambda like when you use it with named_scope. But can this be done for values that are specific to an instance?
In detail it is the has_attached_file method for the paperclip plugin in rails. I want to pass a lambda for the styles hash so that the image styles can be based off of attributes of the object stored in the DB. Is this possible?
Disclaimer: First, the question (Can you pass self to lambda?) and the problem you're trying to solve (dynamic styles with paperclip) don't fully match up. I won't answer the original question because it's not entirely related to your problem, and rampion took a valiant stab at it.
I'll instead answer your paperclip question.
In detail it is the has_attached_file method for the paperclip plugin in rails. I want to pass a lambda for the styles hash so that the image styles can be based off of attributes of the object stored in the DB. Is this possible?
Yes, it is possible. In paperclip, the :styles option can take a Proc. When the attachment is initialized, if a Proc was used, the attachment itself is passed to the Proc. The attachment has a reference to the associated ActiveRecord object, so you can use that to determine your dynamic styles.
For example, your has_attached_file declaration might look something like this (assuming a User and avatar scenario where the user can customize the size of their avatar):
class User < ActiveRecord::Base
has_attached_file :avatar, :styles => lambda { |attachment|
user = attachment.instance
dimensions = "#{user.avatar_width}x#{user.avatar_height}#"
{ :custom => dimensions }
}
end
Ok, you're being unclear.
Local variables in ruby begin with a lowercase letter (like foo, bar, or steve), and are lexically scoped (like C variables). They have nothing to do with "an instance of a class"
Instance variables in ruby begin with an # sigil (like #foo, #bar, or #carl), and are in scope whenever the current value of self is the object they are stored in.
If you want a method that can access the instance variables of an object directly, that's called an instance method. For example, battle_cry and initialize are both instance methods:
class Character
def initialize(name)
#name=name
end
def battle_cry
#name.upcase + "!!!"
end
def Character.default
new("Leeroy Jenkins")
end
end
A class method, by contrast, is a method for a Class object, and doesn't have access to any of the instance variables of that object. In the above example,
default is a class method.
If you want a (class or instance) method that triggers a change in or gets a value from the current scope, ruby uses a type of callback called a block.
class Character
ATTACKS = [ "Ho!", "Haha!", "Guard!", "Turn!", "Parry!", "Dodge!", "Spin!", "Ha", "THRUST!" ]
def attack
ATTACKS.inject(0) { |dmg, word| dmg + yield(word) }
end
end
person = Character.default
puts person.battle_cry
num_attacks = 0;
damage = person.attack do |saying|
puts saying
num_attacks += 1
rand(3)
end
puts "#{damage} points of damage done in #{num_attacks} attacks"
In the above example, attack uses the yield keyword to call the block passed
to it. When we call attack, then, the local variable num_attacks is still
in scope in the block we pass it (delimited here by do ... end), so we can
increment it. attack is able to pass values into the block, here
they are captured into the saying variable. The block also passes values
back to the method, which show up as the return value of yield.
The word lambda in ruby usually means the lambda keyword, which is used
to make blocks into freestanding, function like objects (which themselves are usually
referred to as lambdas, procs, or Procs).
bounce = lambda { |thing| puts "I'm bouncing a #{thing}" }
bounce["ball"]
bounce["frog"]
So I think what you're asking is whether you can pass a Proc in place of a Hash
for an argument to a method. And the answer is "it depends". If the method only
ever uses the #[] method, then yes:
class Character
attr_accessor :stats
def set_stats(stats)
#stats = stats
end
end
frank = Character.new("Victor Frankenstein")
frank.set_stats({ :str => 7, :dex => 14, :con => 9, :int => 19, :wis => 7, :cha => 11 })
monster = Character.new("Frankenstein's Monster")
monster.set_stats(lambda do |stat_name|
rand(20)
end)
However, it might use some other Hash specific methods, or call the same key multiple times,
which can produce weird results:
monster = Character.new("Frankenstein's Monster")
monster.set_stats(lambda do |stat_name|
rand(20)
end)
monster.stats[:dex] #=> 19
monster.stats[:dex] #=> 1
In which case, you may be better off caching the requests in an intermediate hash. This is fairly easy,
since a Hash can have an initializer block. So if we change the above to:
monster.set_stats(Hash.new do |stats_hash, stat_name|
stats_hash[stat_name] = rand(20)
end)
monster.stats[:dex] #=> 3
monster.stats[:dex] #=> 3
The results are cached in the hash
To see more about Hash block initializers, see ri Hash::new:
-------------------------------------------------------------- Hash::new
Hash.new => hash
Hash.new(obj) => aHash
Hash.new {|hash, key| block } => aHash
------------------------------------------------------------------------
Returns a new, empty hash. If this hash is subsequently accessed
by a key that doesn't correspond to a hash entry, the value
returned depends on the style of new used to create the hash. In
the first form, the access returns nil. If obj is specified, this
single object will be used for all default values. If a block is
specified, it will be called with the hash object and the key, and
should return the default value. It is the block's responsibility
to store the value in the hash if required.
h = Hash.new("Go Fish")
h["a"] = 100
h["b"] = 200
h["a"] #=> 100
h["c"] #=> "Go Fish"
# The following alters the single default object
h["c"].upcase! #=> "GO FISH"
h["d"] #=> "GO FISH"
h.keys #=> ["a", "b"]
# While this creates a new default object each time
h = Hash.new { |hash, key| hash[key] = "Go Fish: #{key}" }
h["c"] #=> "Go Fish: c"
h["c"].upcase! #=> "GO FISH: C"
h["d"] #=> "Go Fish: d"
h.keys #=> ["c", "d"]