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Covariance and contravariance real world example
I'm having a little trouble understanding how I would use covariance and contravariance in the real world.
9 Answers
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How to properly create composite primary keys - MYSQL
... gross oversimplification of an intense setup I am working with. table_1 and table_2 both have auto-increment surrogate primary keys as the ID. info is a table that contains information about both table_1 and table_2 .
...
How to use JavaScript regex over multiple lines?
...to match all newlines, you would need to add \r as well to include Windows and classic Mac OS style line endings: (.|[\r\n]).
That turns out to be somewhat cumbersome, as well as slow, (see KrisWebDev's answer for details), so a better approach would be to match all whitespace characters and all no...
Retrieve specific commit from a remote Git repository
... on my PC? The structure of remote repo is absolutely same as that of mine and hence there won't be any conflicts but I have no idea how to do this and I don't want to clone that huge repository.
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How to flatten tree via LINQ?
...er style", convert Flatten to a generic extension method that takes a tree and a function that produces descendants from a node:
public static IEnumerable<T> Flatten<T>(
this IEnumerable<T> e
, Func<T,IEnumerable<T>> f
) => e.SelectMany(c => f(c).Flatten(f)...
LINQ Single vs First
...ou mean the other.
Note: In my code, I will typically use FirstOrDefault() and SingleOrDefault() but that's a different question.
Take, for example, a table that stores Customers in different languages using a Composite Key ( ID, Lang ):
DBContext db = new DBContext();
Customer customer = db.Custome...
Rails extending ActiveRecord::Base
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Create a file in the config/initializers directory called extensions.rb and add the following line to the file:
require "active_record_extension"
Inheritance (Preferred)
Refer to Toby's answer.
Monkey patching (Should be avoided)
Create a file in the config/initializers directory called act...
What can I use instead of the arrow operator, `->`?
... them inconsistently. Becomes really annoying when you work with templates and don't know the precise type.
– Konrad Rudolph
Oct 21 '08 at 10:15
1
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How to automatically crop and center an image
... any arbitrary image, I want to crop a square from the center of the image and display it within a given square.
7 Answers
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What is the difference between Gemfile and Gemfile.lock in Ruby on Rails
I am a beginner to Ruby on Rails and I am using Rails 3.0.9.
3 Answers
3
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