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ActiveRecord, has_many :through, and Polymorphic Associations
...on. :source should points to the polymorphic belongs_to relationship. Then all you need to do is specify :source_type for the relationship you're trying to define.
This fix to the Widget model should allow you do exactly what you're looking for.
class Widget < ActiveRecord::Base
has_many :wid...
What are the benefits of Java's types erasure?
...about type erasure, which is the only thing Java got right, while ignoring all the things it got wrong.
I get huge benefits (e.g. parametricity) and nil cost (alleged cost is a limit of imagination).
new T is a broken program. It is isomorphic to the claim "all propositions are true." I am not big ...
Passing an array by reference
How does passing a statically allocated array by reference work?
5 Answers
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What does Maven Update Project do in Eclipse?
...or doing a project update might revert what you have changed. There are usually some things I have to correct myself anyway though, such as build path exclusions that m2eclipse likes to put in and strange deployment assembly configurations.
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What does the 'L' in front a string mean in C++?
...ry jugement. As a non native English speaker, I can say that I must use it all the time...
– Heyji
May 27 '19 at 19:48
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Removing list of vms in vagrant cache
...s untouched, though. Meaning one still has to unregister and delete it manually. The very simple thing should be that vagrant does its job properly when given $ vagrant destroy -f <id>
– silverdr
Dec 14 '15 at 16:04
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What is the fastest or most elegant way to compute a set difference using Javascript arrays?
Let A and B be two sets. I'm looking for really fast or elegant ways to compute the set difference ( A - B or A \B , depending on your preference) between them. The two sets are stored and manipulated as Javascript arrays, as the title says.
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How to use relative/absolute paths in css URLs?
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Personally, I would fix this in the .htaccess file. You should have access to that.
Define your CSS URL as such:
url(/image_dir/image.png);
In your .htacess file, put:
Options +FollowSymLinks
RewriteEngine On
RewriteRule ^ima...
Convert a Unicode string to a string in Python (containing extra symbols)
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This breaks if the content of the string is actually unicode, not just ascii characters in a unicode string. Don't do this, you'll get random UnicodeEncodeError exceptions all over the place.
– Doug
Oct 9 '13 at 7:31
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Pandas conditional creation of a series/dataframe column
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List comprehension is another way to create another column conditionally. If you are working with object dtypes in columns, like in your example, list comprehensions typically outperform most other methods.
Example list comprehension:
df['color'] = ['red' if x == 'Z' else 'green' for x in d...