My goal is to add +1 every day to a global variable in Firebase to track how many days have passed. I'm building an app that give new facts every day, and at the 19:00 UTC time marker, I want the case statement number (the day global day variable) to increment by +1.
Some have suggested that I compare two dates and get the days that have passed that way. If I were to do that, I could hard code the initial time when I first want the app to start at 19:00 some day. Then when the function reached1900UTC() is called everyday thereafter, compare it to a Firebase timestamp of that current time which should be 19:00. In theory, it should show that 1 day or more day has passed.
This is the best solution so far, thanks to #DavidSeek and #Jay, but I would still like to figure it out with concurrent writes if anyone has a solution in that front. Until then, I'm marking David's answer as the correct one.
How would I make it so it can't increase more than +1 if multiple people call this? Because my fear is that, when say, 100 people calls this function, it increases by + 1 for every person that has called it.
My app works on a global time, and this function is called every day at 19:00 UTC. So when that function is called I want the day count to increase by one.
You should use transactions to handle concurrent writes:
https://firebase.google.com/docs/database/ios/read-and-write#save_data_as_transactions
You may know this but Firebase doesn't have a way to auto-increment a counter as there's no server side logic, so having a counter increment at 19:00 UTC isn't going to be possible without interaction from a client that happens to be logged on at that time.
That being said, it's fairly straightforward to have the first user that logs in increment that counter - then any other clients logging in after that would not increment it and would have access to that day's new content.
Take a look at Zapier.com - that's a service that can fire time based triggers for your app which may do the trick.
As of this writing, Zapier and Firebase don't play nice together, however, there are a number of other trigger options that Zapier can do with your app while continuing to use Firebase for storage.
One other thought...
Instead of dealing with counters and counting days, why not just have each day's content stored within a node for each day and when each user logs on, the app get's that days content:
2016-10-10
fact: "The Earth is an Oblate Spheroid"
2016-10-11
fact: "Milli Vanilli is neither a Milli or a Vanilli. Discuss."
2016-10-12
fact: "George Washington did not have a middle name"
This would eliminate a number of issues such as counters, updates, concurrent writing to Firebase, triggers etc.
It's also dynamic and expandable and a user could easily see that day's facts or the fact for any prior day(s)
I'm trying to split your question into different sections.
1) If you want to use a global variable to count the days from, let's say, today. Then I would set a timestamp hardcoded into the App that sets the NSDate.
Then In my App, when I need to know the days that have been passed by, I would call a function counting the days from the timestamp to NSDate().
2) If you have a function in your App that counts a +1 into a Firebase, then your fear is correct. It would count +1 for every person that uses the App.
3) If you want every User to have a variable count since when they use their App, then I would handle User registration. So I have a "UserID" and then I would set a Firebase tree like that:
UserID
------->
FirstOpen
-------> Date
That way you could handle each User's first open.
Then you are able to set a timestamp AND call +1 for every user independently. Because then you set the +1 for every user into their UserID .child
Related
I have an aggregation that looks at a sliding 30-day window (1 day period) of customer purchases, keyed by customer id, with the value being the purchase amount. I sum up the values by key, thus getting the aggregate purchase amount for each customer during the last 30 days. I store this number in a customer record in an external database.
My question is this: if a customer hasn't purchased anything in the last 30 days, how do I automatically reset the customer record to a default value, in this case zero? I'd prefer to keep all my logic in Dataflow and avoid doing too much work, since this will need to scale quite a bit. I'm basically looking for a way to automatically get a key-value for each key that was not in the current window but was in the last, and the value being a potentially configurable default.
Trying to answer my own question, but hoping for feedback as to whether this solution would scale:
I've thought about having a step after the initial window-and-sum. This transform would receive (customerId, purchaseSum) elements once a day, as the result of the 30-day window sum is made available. Since these elements are timestamped (with the timestamp of the most recent input element, I believe) I can re-window them. If I create a two-day window with a one-day period, I would then be able to group by key and process (customerId, [purchaseSumA, purchaseSumB]) for customers that had a purchase both in the last 30 days and in the last 31 days. In this case, I emit purchaseSumB. However, if there's only in element in the list, and the timestamp indicates that the purchase was made 31 days ago, I can assume that there were no purchases from the customer since, and I need to emit (customerId, 0). Does that make sense?
Is it an option to slightly amend the database schema? I suppose now you have something like
(customer_id int, purchases_last_month int)`
Instead how about
`(customer_id int, last_purchase datetime, purchases_last_month int)`
where this time last_purchase is the time of the last purchase made by this customer, and purchases_last_month refers to purchases made in the month before the last one? Then in your DoFn that writes to the database, you'd be making a conditional update (merge/upsert) that updates both last_purchase and purchases_last_month with the values from the current window, but only if last_purchase is increasing. This way you can deal with windows being processed out-of-order or in parallel, at the cost of slight increase in complexity in client queries (which you can address by adding a view on top of the table).
Background info: I have a simple tally counter/habit-tracking app that populates a tableview with custom cells - the counters. Tapping on a cell brings up a detailed view of a specific counter that has the name, value, and the time period for that counter (daily/weekly/monthly/yearly/total). I have also stored in CoreData the startDate and endDate for each counter, so each counter resets after a certain time.
What I would like to do: Each time a counter resets (e.g. after a day or a week), I would like its current total value to be added to a log (preferably some sort of array) specific to that counter. This will then populate another tableview so that, after a few weeks, I can look back and see the previous weekly totals and compare it to the current week.
My data structure:
Entity: Counter
Attributes: Value (Int), startDate(NSDate), endDate(NSDate), timePeriod(Int) (Note: For timePeriod, each integer from 0 to 4 represents daily/weekly/monthly/yearly/no reset.)
My question: How can I implement this? Do I create another entity with a date and value attribute that is created each time a counter resets? I'm having trouble visualizing how to do this with CoreData.
P.S. I don't think using tableview and fetch requests is what I'm looking for.
Thanks so much for your help, and ask me if you need any clarification!
The simplest way is to not "reset" the counter but create a new one. You can then easily display the past counters. That would avoid creating a new entity.
To make it even simpler to distinguish them from active counters you could add a flag like active or archived. You could use that flag for a convenient predicate in your fetched results controller.
I am using CMStepCounter and CMMotionActivityManager.
What I would like to do is work out my total walking time throughout the day, and from this, my average speed.
However, looking at the data in CMMotionActivityManager, it is clear than a number of steps throughout the day are actually logged during periods that are of 'unknown activity' and not walking or running. This does make sense, as you need to do a handful of steps for iOS to know you are walking. However, these add up over the course of any given day.
Querying CMMotionActivity, it is possible to get the timestamp of every event. However, whilst it is clear to me that every step must be timestamped in CMStepCounter, I can only see a method to return the total number of steps between two points in time. What would be great is if I could return an array of every step with its time stamp, and if so, how?
Many thanks.
With the current Core Motion API, you can't get an array of every step with its time stamp directly.
But you can use queryActivityStartingFromDate:toDate:toQueue:withHandler: to get an array of CMMotionActivity objects. Then use the time stamps to calculate the number of steps by calling queryStepCountStartingFrom:to:toQueue:withHandler:.
I don't think the M7 processor stores every step with its own time stamp. If you pass 1 as stepCounts to the method startStepCountingUpdatesToQueue:updateOn:withHandler:, you'll notice the handler is not executed on every step. Like the document says: The handler block is executed on a best effort basis each time the step count threshold is exceeded.
I am to store quite large amount of boolean values in database used by Rails application - it needs to store 60 boolean values in single record per day. What is best way to do this in Rails?
Queries that I will need to program or execute:
* CRUD
* summing up how many true values are for each day
* possibly (but not nessesarily) other reports like how often true is recorded in each of field
UPDATE: This is to store events that may or may not occur in 5 minute intervals between 9am and 1pm. If it occurs, then I need to set it to true, if not then false. Measurements are done manually and users will be reporting these information using checkboxes on the website. There might be small updates, but most of the time it's just one time entry and then queries as listed above.
UPDATE 2: 60 values per day is per one user, there will be between 1000-2000 users. If there isn't some library that helps with that, I will go for simplest approach and deal with it later if I will get issues with performance. Every day user reports events by checking desired checkboxes on the website, so there is normally a single data entry moment per day (or few if not done on daily basis).
This is dependent on a lot of different things. Do you need callbacks to run? Do you need AR objects instantiated? What is the frequency of these updates? Is it done frequently but not many at a time or rarely but a bunch at once? Could you represent these booleans as a mask instead? We definitely need more context.
Why do these need to be in a single record? Can't you use a 'days' table to tie them all together, then use a day_id column in your 'events' table?
Specify in the Day model that it 'has_many :events' and specify in the Event model file that it 'belongs_to :day'. Then you can find all the events for a day with just the id for the day.
For the third day record, you'd do this:
this_day = Day.find 3
Then you can you use 'this_day.events' to get all the events for that day.
You'll need to decide what you wish to use to identify each day so you query for a day's events using something that you understand. The id column I used above to find it probably won't work.
You could use the timestamp first moment of each day to do that, for example. Or you could rely upon the 'created_at' column of the table to be between the start and end of a day
And you'll want to be sure to thing about what time zone you are using and how this will be stored in the database.
And if your data will be stored close to midnight, daylight savings time could also be an issue. I find it best to use GMT to avoid that issue.
Good luck.
What I want to do is very simple but I'm trying to find the best or most elegant way to do this. The Rails application I'm building now will have a schedule of daily classes. For each class the fields relevant to this question are:
Day of the week
Starting time
Ending time
A single entry could be something such as:
day of week: Wednesday
starting time: 10:00 am
ending time: Noon
Also I must mention that it's a bi-lingual Rails 2.2 app and I'm using the native i18n Rails feature. I actually have several questions.
Regarding the day of the week, should I create an extra table with list of days, or is there a built-in way to create that list on the fly? Keep in mind these days of the week will have to be rendered in English or Spanish in the schedule view depending on the locale variable.
While querying the schedule I will need to group and order the results by weekday, from Monday to Sunday, and of course order the classes within each day by starting time.
Regarding the starting time and ending time of each class would you use datetime fields or integer fields? If the latter how would you implement this exactly?
Looking forward to read the different suggestions you guys will come up with.
I would just store the day of the week as an integer. 0 => Monday ... 6 => Sunday (or any way you want. ie. 0 => Sunday). Then store the start time and end time as Time.
That would make grouping really easy. All you would have to do is sort by the day of the week and the start time.
You can display this in multiple ways, but here is what I would do.
Have functions like: #sunday_classes = DailyClass.find_sunday_classes that returns all the classes for Sunday sorted by start time. Then repeat for each day.
def find_sunday_classes
find_by_day_of_week(1, :order -> 'start_time')
end
Note: find_by probably should have id at the end but that's just preference in how you want to name the column.
If you want the full week then call all seven from the controller and loop trough them in the view. You could even create detail pages for each day.
Translation is the only tricky part. You can create a helper function that takes an integer and returns the text for the appropriate day of the week based on local.
That's very basic. Nothing complicated.
If your data is a Time then I would store that as a Time - otherwise you will always have to convert it out of the database when you do date and time related operations on it. The day is redundant data, as it will be part of the time object.
This should mean that you don't need to store a list of days.
If t is a time then
t.strftime('%A')
will always give you the day as a string in English. This could then be translated by i18n as required.
So you only need to store starting time and ending time, or starting time and duration. Both should be equivalent. I would be tempted to store ending time myself, in case you need to do data manipulations on ending times, which therefore won't have to be calculated.
I think most of the rest of what you describe should also fall out of storing time data as instances of Time.
Ordering by week day and time will just be a matter of ordering by your time column. i.e.
daily_class.find(:all, :conditions => ['whatever'], :order => :starting_time)
Grouping by day is a little more tricky. However this is an excellent post on how to group by week. Grouping by day will be analogous.
If you are dealing with non-trivial volumes of data, it may be better to do it in the database, with a find_by_sql and that may depend on your database's time and date functionality, but again storing the data as a Time will also help you here. For example in Postgresql (which I use), getting the week of a class is
date_trunc('week', starting_time)
which you can use in a Group By clause, or as a value to use in some loop logic in rails.
Re days-of-week, if you need to have e.g. classes that meet 09:00-10:00 on MWF, then you could either use a separate table for days a class meets (keyed by both class ID and DOW) or be evil (i.e. non-normalized) and keep the equivalent of an array of DOW in each class. The classic argument is this:
The separate table can be indexed in a way to support either class-oriented or DOW-oriented selects, but takes a bit more glue to put the entire picture together for a class.
The array-of-DOW is simpler to visualize for beginning programmers and slightly simpler to code about, but means that reasoning about DOW requires looking at all classes.
If this is only for your personal class schedule, do what gets you the value you're looking for, and live with the consequences; if you're trying to build a real system for multiple users, I'd go with a separate table. All those normalization rules are there for a reason.
As far as (human-readable) DOW names, that's a presentation-layer issue, and shouldn't be in the core concept of DOW. (Suppose you decided to move to Montreal, and needed French? That should be another "face" and not a change to the core implementation.)
As for starting/ending times, again the issue is your requirements. If all classes begin and end at hour (x:00) boundaries, you could certainly use 0..23 as the hours of the day. But then your life would be miserable as soon as you had to accommodate that 45-minute seminar. As the old commercial said, "Pay me now or pay me later."
One approach would be to define your own ClassTime concept and partition all reasoning about times to that class. It could start with a simplistic representation (integral hours 0..23, or integral minutes after midnight 0..1439) and then "grow" as needed.