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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...
is there a css hack for safari only NOT chrome?
...3 (early 2020 Update) *
PLEASE PLEASE -- If you are having trouble, and really want to get help or help others by posting a comment about it, Post Your Browser and Device (MacBook/IPad/etc... with both browser and OS version numbers!)
Claiming none of these work is not accurate (and actually not ev...
Checking for empty queryset in Django
...if not my_objects: to demonstrate that this is how they do it in the docs. All else is utterly irrelevant so I do not get your point. They could as well make a thousand queries and it would still be totally irrelevant as this is not the point of this answer, with which I make clear that I agree.
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How to get current timestamp in milliseconds since 1970 just the way Java gets
...e UNIX epoch, but the spec only says it must be the system-wide real time wall clock. There is no requirement for the steady_clock to match reality, only that it only move forward.
– Oz.
Jul 27 '15 at 23:22
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How to find out what type of a Mat object is with Mat::type() in OpenCV
...";
r += (chans+'0');
return r;
}
If M is a var of type Mat you can call it like so:
string ty = type2str( M.type() );
printf("Matrix: %s %dx%d \n", ty.c_str(), M.cols, M.rows );
Will output data such as:
Matrix: 8UC3 640x480
Matrix: 64FC1 3x2
Its worth noting that there are also Matr...
What is an undefined reference/unresolved external symbol error and how do I fix it?
... token is converted into a token. (2.7). The
resulting tokens are syntactically and semantically analyzed and
translated as a translation unit. [SNIP]
Translated translation units and instantiation units are combined as follows: [SNIP]
All external entity references are resolved. Library components ...
How to get the return value from a thread in python?
...ram in param_list] The order will be maintained, and exiting the with will allow result collection. [f.result() for f in futures]
– jayreed1
Jun 4 at 21:29
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Regex lookahead, lookbehind and atomic groups
...ely follow, and stop as backtracking is disabled
A non-atomic group will allow backtracking; if subsequent matching ahead fails, it will backtrack and use alternative patterns until a match for the entire expression is found or all possibilities are exhausted.
(foo|foot)s applied to foots will:
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ObservableCollection not noticing when Item in it changes (even with INotifyPropertyChanged)
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The ContentList's Set method will not get called when you change a value inside the collection, instead you should be looking out for the CollectionChanged event firing.
public class CollectionViewModel : ViewModelBase
{
public ObservableCollection<E...
mongodb group values by multiple fields
... $slice just off the basic aggregation result. For "large" results, run parallel queries instead for each grouping ( a demonstration listing is at the end of the answer ), or wait for SERVER-9377 to resolve, which would allow a "limit" to the number of items to $push to an array.
db.books.aggregate(...