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Determine what attributes were changed in Rails after_save callback?

I'm setting up an after_save callback in my model observer to send a notification only if the model's published attribute was changed from false to true. Since methods such as changed? are only useful before the model is saved, the way I'm currently (and unsuccessfully) trying to do so is as fol...
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C# Lazy Loaded Automatic Properties

... 4.0 Lazy<T> type to create this pattern private Lazy<string> _someVariable =new Lazy<string>(SomeClass.IOnlyWantToCallYouOnce); public string SomeVariable => _someVariable.Value; This code will lazily calculate the value of _someVariable the first time the Value expression i...
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Android Notification Sound

...n Codeding String en_alert, th_alert, en_title, th_title, id; int noti_all, noti_1, noti_2, noti_3, noti_4 = 0, Langage; class method Intent intent = new Intent(context, ReserveStatusActivity.class); PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0); Notificati...
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Which is faster in Python: x**.5 or math.sqrt(x)?

... I've now run it 3 times on codepad.org and all three times a() was much faster than b(). – Jeremy Ruten Nov 29 '08 at 1:38 13 ...
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How do I enable EF migrations for multiple contexts to separate databases?

... The 2nd call to Enable-Migrations is failing because the Configuration.cs file already exists. If you rename that class and file, you should be able to run that 2nd Enable-Migrations, which will create another Configuration.cs. You ...
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ng-app vs. data-ng-app, what is the difference?

... It seems like such a waste of CPU cycles to manually strip off data- and x-. Why can't the HTML validation rules be changed to accept ng- stuff? – DaveAlger May 13 '15 at 14:43 ...
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How to export data as CSV format from SQL Server using sqlcmd?

...th '""' + col1 + '""' AS col1, wrapped in (doubled) double quotes or just call a stored procedure. – MisterIsaak Dec 11 '13 at 17:17 ...
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Getting the class name from a static method in Java

...tatic context to mean the current Class in Java, that that "class.xxx" was allowed in either instance or static code to mean this class! The problem with this is that MyClass is verbose and redundant, in the context. But then as much as I like Java it does seem to lean towards verbosity. ...
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How to read a large file - line by line?

... The for line in f treats the file object f as an iterable, which automatically uses buffered I/O and memory management so you don't have to worry about large files. There should be one -- and preferably only one -- obvious way to do it. ...
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Extract month and year from a zoo::yearmon object

... Ha thank you for this answer. It especially beats the other solutions when you want to do something like if(year(date1) > 2014){year(date1) <- year(date1) - 100} – Vincent Feb 10 '14 at 9:34 ...