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Rails :dependent => :destroy VS :dependent => :delete_all
...e is an instantiation of all of your children. So, if you can't destroy it or if each has their own :dependent, its callbacks can be called.
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How do I include related model fields using Django Rest Framework?
...assroom
depth = 1
However, that will only include relationships for forward relationships, which in this case isn't quite what you need, since the teachers field is a reverse relationship.
If you've got more complex requirements (eg. include reverse relationships, nest some fields, but no...
Why can I throw null in Java? [duplicate]
...ttempting to throw null itself throws a NullPointerException.
In other words, throw checks that its argument is nonnull, and if it is null, it throws a NullPointerException.
JLS 14.18 specifies this behavior:
If evaluation of the Expression completes normally, producing a null value, then an...
Running multiple commands in one line in shell
...direct the output of a command into another command. What you are looking for is && operator to execute the next command only if the previous one succeeded:
cp /templates/apple /templates/used && cp /templates/apple /templates/inuse && rm /templates/apple
Or
cp /template...
Gradient of n colors ranging from color 1 and color 2
I often work with ggplot2 that makes gradients nice ( click here for an example ). I have a need to work in base and I think scales can be used there to create color gradients as well but I'm severely off the mark on how. The basic goal is generate a palette of n colors that ranges from x colo...
Clone only one branch [duplicate]
... how I could clone only one branch instead of cloning the whole Git repository.
4 Answers
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Update MongoDB field using value of another field
... aggregation pipeline in the update document and the updateOne, updateMany or update collection method. Note that the latter has been deprecated in most if not all languages drivers.
MongoDB 4.2+
Version 4.2 also introduced the $set pipeline stage operator which is an alias for $addFields. I will...
Does Git Add have a verbose switch
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For some git-commands you can specify --verbose,
git 'command' --verbose
or
git 'command' -v.
Make sure the switch is after the actual git command. Otherwise - it won't work!
Also useful:
git 'command' --dry-run
...
What is the difference between include and extend in Ruby?
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What you have said is correct. However there is more to it than that.
If you have a class Klazz and module Mod, including Mod in Klazz gives instances of Klazz access to Mod's methods. Or you can extend Klazz with Mod giving the class Klazz access...
How do I use CMake?
I am trying to use CMake in order to compile opencv.
4 Answers
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