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How do you delete an ActiveRecord object?
...
It's destroy and destroy_all methods, like
user.destroy
User.find(15).destroy
User.destroy(15)
User.where(age: 20).destroy_all
User.destroy_all(age: 20)
Alternatively you can use delete and delete_all which won't enforce :before_destroy and :after...
Macro vs Function in C
...uct webpage page;
page.numButtons = 2;
num_button_holes(page) -> 8
Finally, macros can be difficult to debug, producing weird syntax errors or runtime errors that you have to expand to understand (e.g. with gcc -E), because debuggers cannot step through macros, as in this example:
#define prin...
Behaviour of increment and decrement operators in Python
...e applied on a variable (like ++count ). It compiles, but it does not actually change the value of the variable!
9 Answers...
How to find list intersection?
... looking for a slightly different animal - and you may need to do that manually by sorting each list and merging the results - and keeping dups in the merging.
– javadba
Jan 6 '19 at 18:51
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Qt: can't find -lGL error
I just reinstalled QtCreator, created new project ( Qt Application ) an got this after compilation:
8 Answers
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Javascript - How to detect if document has loaded (IE 7/Firefox 3)
I want to call a function after a document loads, but the document may or may not have finished loading yet. If it did load, then I can just call the function. If it did NOT load, then I can attach an event listener. I can't add an eventlistener after onload has already fired since it won't get cal...
How to use base class's constructors and assignment operator in C++?
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You can explicitly call constructors and assignment operators:
class Base {
//...
public:
Base(const Base&) { /*...*/ }
Base& operator=(const Base&) { /*...*/ }
};
class Derived : public Base
{
int additional_;
public:
...
How does the algorithm to color the song list in iTunes 11 work? [closed]
...y discovered that the built-in Mathematica function DominantColors doesn't allow enough fine-grained control to approximate the algorithm that iTunes uses. I wrote my own function instead...
A simple method to calculate the dominant color in a group of pixels is to collect all pixels into buckets ...
setup.py examples?
...through Python packages on the Python Package Index. Just download the tarball, unpack it, and have a look at the setup.py file. Or even better, only bother looking through packages that list a public source code repository such as one hosted on GitHub or BitBucket. You're bound to run into one on t...
Hash Map in Python
...res the keys to strings which are also valid Python identifiers (and internally, this also creates a dictionary).
– user395760
Jan 2 '12 at 17:31
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