I want to initialize a variable in rails and use it in a controller's action, but the variable should have a fixed value when the server starts. I have tried defining it inside a controller's action and it get's the same initialized value for every request. For example, i want to initialize a date.now and have the same date after 15 days also.
Update
I am implementing a coming soon page in which a timer is shown 15 days from now. If i implement it in a action inside a controller, it shows new date every time the action is invoked.
Please Help
If you want to create a CONSTANT in rails then you can simply put it into the initializer file. For eg, create a file name constants.rb inside initializer:
#config/initializers/constants.rb
TEST_VALUE = 10
And to access this CONSTANT from your controller, just call for TEST_VALUE. for eg,
#controllers_path/some_controller.rb
.....
def some_def
#value = TEST_VALUE # this will be enough to fetch the constants.
end
But, make sure you restart your server after changing the intializer.
You're looking to create a constant, which is basically a variable which doesn't change its value
You'd typically set these with initializers:
#config/initializers/your_initializer.rb
YOUR_CONSTANT = your_date
To maintain a persistent date, you'll have to give some more context on what you're using it for. It will be difficult to create this each time Rails loads (how to know which Time.now to use), so giving us more info will be a good help
You can also use an opposite approach. Assuming you should know the date when the new feature comes (for example 2014-04-04 18:00) you can just find a number of seconds left till the target date:
#seconds_left = Time.parse('2014-04-04 18:00').to_i - Time.now.to_i
then pass it to client side and implement a timer. So you'll just need to store a string representation of a target date.
Obvious disadvantage of this approach is that you should adjust that target time each time you want to introduce a new feature.
Related
What is the best way with Rails to have a “time” attribute (selected by the user) which is supposed to always be displayed as the same “static” time value?
(Meaning: It should always show the same time, for example “14:00”, completely independently of any user’s time zone and/or DST value.)
Until now, I have tried the following setup:
In the MySQL database, I use a field of the type time (i.e. with the format: 14:00:00)
In the Rails view, I use the helper time_select (because it’s really handy)
However, it seams that with this approach, Rails’ ActiveRecord will treat this time value as a full-blown Ruby Time object, and therefor convert the value (14:00:00) to the default time zone (usually set to ‘UTC’) for storage and then convert it back to the user’s time zone, for the view. And if I’m not mistaken, this also means that the fluctuating DST value will make the displayed time value fluctuate throughout the year (and the same happens if the user moves to another time zone).
So what is the best way to manage a simple “static” time attribute with Rails?
If you don't want any time related functionality, why not save it as an string field. Since from your question description its evident that functionalities such as timezone doesn't effect your use case, so just make it a normal VARCHAR(8) and save the value as a string and parse it such as Time.now.strftime("%H:%M:%S") before saving it to the database, you can also write this logic inside your ActiveRecrd model class
def static_time=(value)
super(value.strftime("%H:%M:%S"))
end
you can somewhere in the code say model_object.static_time=Time.now and this will automatically parse it, if you want to get the time as a ruby object retaining the format you can simply do it defining a custom getter.
def static_time
current_time = Time.now
time_keys = [:hour, :min, :sec]
current_time.change(**Hash[time_keys.zip(super.split(":"))])
end
I am developing a rails app. Most of the parts work fine, but I got one weird problem when I tried to calculate the time an user used to edit and submit one form.
I thought it would be good to do it in the following order:
1. in the controller "edit" method, record the time the user start to see the form.
2. in the "update" method, record the submit time, then do the math and get how long the user had spent on the form.
class Test
##start_time = 0
##end_time = 0
def edit
##start_time = Time.now
end
def update
##end_time = Time.now
time_used = ##end_time - ##start_time
puts time_used.to_i
end
end
The code above actually works fine while running on my own developing computer, the output is what I expected. But when I upload the code to the production environment(multicore cpus), sometime the output is right, sometime it is not. I debugged the code and found in some case, the ##start_time is set to 0 when submitting the form. I am confused what was going on, maybe I just misused the ## for the variable. Please help me out, any idea would be appreciated, thanks.
Edit:
The problem is solved by adding a virtual attribute to the model as hinted by Vishal. In addition, I added a hidden field in the submit form, and in the strong parameter part added the corresponding parameter to allow it to be passed from edit to update method.
Your solution will create conflicts when more than two users try to edit simultaneously, So basically what idea I have is:
Add one virtual attribute in your model edit_start_time You don't need attribute for endtime because it can be directly fetched by Time.now at any time.
Set edit_start_time value in edit method like:
#model.edit_start_time = Time.now.utc #you can use any
In update method directly calculate edit time like:
total_update_time = Time.now.utc - #model.edit_start_time.utc
If you are unaware of how to create virtual attributes then there are so many questions on StackOverflow as well as docs. I am not explaining how to do it here because its the different topic.
All the best
You're using class variables that can interfer with each other. Your Test class will only ever have one class variable called ##start_time associated with it.
This means if another user sees the form, they will reset the ##start_time for every user currently on it.
To prevent this, use instance varaibles. When a new user sees the form, they will make a new instance variable that is tied to their instance of the class, rather than the class itself. This will allow users to have different start and end times.0
All you need to do is change every ## to #. So instead of ##start_time', try#start_time` throughout your code, and the same for end_time.
I'm prototyping an app and want to have a global variable that I can hit an endpoint that toggles the global variable $current_status. I have:
def toggle_status
$current_status=false if $current_status.nil?
$current_status=!$current_status
r={}
r[:current_status]=$current_status
render json:r.to_json
end
and in application_controller.rb
class ApplicationController < ActionController::Base
protect_from_forgery with: :exception
$current_status
end
but hitting /toggle_status always returns false. Why isn't assigning a bool to what it isn't changing this value? I'm aware something like this should be in db but just prototyping
edit 1
I just created this in lib/
class Jt
#cur
def self.cur
#cur
end
def self.cur=val
#cur=val
end
end
and updated the controller to:
def toggle_status
Jt.cur=!Jt.cur
r={}
r[:current_status]=Jt.cur
render json:r.to_json
end
Your toggle code doesn't actually toggle anything. It appears you expect this line to "toggle" the contents of the $current_status variable.
$current_status!=$current_status
However, the != operator doesn't assign anything but it is a comparison operator. In your case, it returns always false based on your query whether $current_status is equal to not $current_status.
What you want to use instead is probably
$current_status = !$current_status
As for your software design, global variables are generally frowned upon in Ruby (and Rails) as are all other kinds of globally mutable state. Use proper classes and objects instead to encapsulate your state and behaviour into more manageable structures. Using global variables, you will shoot yourself in the foot some day and you will have a very hard time to find out what is actually happening. You should try to avoid this :)
You can't use a global variable in this way in such app and there are several reasons. I'll give you just one: depending on the webserver you use, the server may start different processes to handle the incoming web requests, and global variables can't be shared between these processes.
And in fact, it's not even a good idea to use a global variable at all.
If you want to persist a state, use a proper storage. Depending on how long the value should be persisted and who should be able to access it, you have plenty of choices:
database
file system
memory
cookie
Your first snipper does not work because != is a comparison operator, not assignment
Second may not work due to code reloading (Jt class instance is not guaranteed to be the same for other request unless cache_classes is on, but in development you usually always want it off, because otherwise any code changes require server restart to take effect), simple way to have a non-reloaded class - put it in a initializer
For prototyping you also may try thread-local storage for this task: Thread.current[:foo] = 1234
I am having following function to find some of the selected records from public pages.
def find_public_page(title)
#footer_public_pages ||= PublicPage.where(title: %w(welcome_to_toylist terms_of_services buying_a_toy selling_a_toy requesting_a_toy ad_guildelines))
#footer_public_pages.find_by(title: title)
end
what I need is that #footer_public_pages should store the result set in first time and then on next time it will directly hit the find_by query instead of firing two queries.
Any help would be appreciated.
You can try this. I hope this will help You.
def find_public_page(title)
#footer_public_pages ||= PublicPage.where(title: %w(welcome_to_toylist terms_of_services buying_a_toy selling_a_toy requesting_a_toy ad_guildelines)).group_by(&:title)
#footer_public_pages[title].first unless #footer_public_pages[title].blank?
end
The instance variable #footer_public_pages belongs to a class, in this case probably the controller. Because of the way the controller works, every action (i.e. redirect) is going to be a new instance, and will need to set that value again on calling find_public_page. The way it's currently coded would help you if you were calling the method multiple times in the same action (and/or its views), but I doubt that is the case. Instead, if you're trying to keep this variable across multiple pages, you'll want to use a session variable. So you could say:
def find_public_page(title)
session[:footer_public_pages] ||= PublicPage.where(title: %w(welcome_to_toylist terms_of_services buying_a_toy selling_a_toy requesting_a_toy ad_guildelines))
session[:footer_public_pages].find_by(title: title)
end
If you follow this approach, just be warned that these session variables will only be dumped when the user closes the browser (NOT when they navigate away from your site), so you have to be careful in managing them.
I have to compare the date in rails to get the values after that date I have send the date as "2013-03-04T06:26:25Z"but actually the record in the db contains date as follows 2013-03-04 06:26:25.817149 so when i check with the date it also returns that record but i want records after that date. how can i remove the milliseconds from the db? please help me.
I had a similar problem
Update your time object like this before sending it to the database :
time.change(:usec => 0)
Since ruby 1.9 you can use round
t = Time.now.round
t.usec # => 0
I was also having this problem, however when I was applying the change as indicated in #Intrepidd's answer, it wasn't affecting the microseconds of my time object.
Please note that (at least currently) the :usec key only works with the Time#change method, and not with the DateTime#change method.
The DateTime#change method ignores the keys that it doesn't accept, so you wouldn't be able to tell that your attempted change of the microseconds didn't work unless you inspected the object further (such as with DateTime#rfc3339(9)).
So before you attempt this change, make sure that you are working with a Time object, not a DateTime object.