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Ruby on Rails Callback, what is difference between :before_save and :before_create?
Could you explain in detail what the :before_save and :before_create Ruby on Rails callbacks are, and what they have to do with Rails validations? Does validation occur after :before_save or :before_create ?
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Why does an image captured using camera intent gets rotated on some devices on Android?
I'm capturing an image and setting it to image view.
24 Answers
24
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What is the fundamental difference between WebSockets and pure TCP?
I've read about WebSockets and I wonder why browser couldn't simply open trivial TCP connection and communicate with server like any other desktop application. And why this communication is possible via websockets?
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How do I generate a random int number?
How do I generate a random integer in C#?
32 Answers
32
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What is an invariant?
... of a program state that is always true..." - @jacob baskin - well written and thanks for this.
– twknab
May 31 '19 at 23:37
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How to add 'ON DELETE CASCADE' in ALTER TABLE statement
...ON DELETE CASCADE to an already existing constraint. You will have to drop and re-create the constraint. The documentation shows that the MODIFY CONSTRAINT clause can only modify the state of a constraint (i-e: ENABLED/DISABLED...).
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Amazon EC2, mysql aborting start because InnoDB: mmap (x bytes) failed; errno 12
.... Since Micro instances have only 613MB of memory, MySQL crashed every now and then. After a long search about MySQL, Micro Instance and Memory Managment I found out there is no default SWAP space for Micro instance. So if you want to avoid the crash you may need to setup a swap space for your micro...
JavaScript: What are .extend and .prototype used for?
I am relatively new to JavaScript and keep seeing .extend and .prototype in third party libraries I am using. I thought it had to do with the Prototype javascript library, but I am beginning to think that is not the case. What are these used for?
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'float' vs. 'double' precision
... in C use IEEE 754 encoding.
This type of encoding uses a sign, a significand, and an exponent.
Because of this encoding, many numbers will have small changes to allow them to be stored.
Also, the number of significant digits can change slightly since it is a binary representation, not a decimal ...
Sql Server 'Saving changes is not permitted' error ► Prevent saving changes that require table re-cr
When I create a table in SQL Server and save it, if I try to edit the table design, like change a column type from int to real, I get this error:
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