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How can i tell if an object has a key value observer attached
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Put a try catch around your removeObserver call
@try{
[someObject removeObserver:someObserver forKeyPath:somePath];
}@catch(id anException){
//do nothing, obviously it wasn't attached because an exception was thrown
}
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Move capture in lambda
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Generalized lambda capture in C++14
In C++14 we will have the so called generalized lambda capture. This enables move capture. The following will be legal code in C++14:
using namespace std;
// a unique_ptr is move-only
auto u = make_unique<some_type>( some, parameters );
// move...
Select distinct values from a table field
...ant any ordering to be applied to a query, not even the default ordering, call order_by() with no parameters.
and distinct() in the note where it discusses issues with using distinct() with ordering.
To query your DB, you just have to call:
models.Shop.objects.order_by().values('city').distinct(...
addEventListener vs onclick
...se);
Using this approach (DOM Level 2 events), you can attach a theoretically unlimited number of events to any single element. The only practical limitation is client-side memory and other performance concerns, which are different for each browser.
The examples above represent using an anonymous...
How to convert nanoseconds to seconds using the TimeUnit enum?
... This answer is now wrong - convert() and the toFoo() methods all return longs now docs.oracle.com/javase/6/docs/api/java/util/concurrent/…
– Riking
Jul 30 '13 at 1:58
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Why call git branch --unset-upstream to fixup?
.... Once local branch L is set to track remote-tracking branch R, Git will call R its "upstream" and tell you whether you're "ahead" and/or "behind" the upstream (in terms of commits). It's normal (even recommend-able) for the local branch and remote-tracking branches to use the same name (except fo...
Simple Digit Recognition OCR in OpenCV-Python
...stand some of the features at end)
2) Since I knew, without understanding all those features, it is difficult to do that method. I tried some other papers, but all were a little difficult for a beginner.
So I just decided to take all the pixel values as my features. (I was not worried about accura...
Getting attributes of a class
...gt;> inspect.getmembers(MyClass, lambda a:not(inspect.isroutine(a)))
[('__class__', type),
('__dict__',
<dictproxy {'__dict__': <attribute '__dict__' of 'MyClass' objects>,
'__doc__': None,
'__module__': '__main__',
'__weakref__': <attribute '__weakref__' of 'MyClass' obje...
Add Variables to Tuple
... I think its important to note that tuples are immutable - they cannot actually be modified. What this solution does is create a new tuple based on two existing tuples.
– That1Guy
Jan 16 '19 at 20:58
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Do sealed classes really offer performance Benefits?
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The JITter will sometimes use non-virtual calls to methods in sealed classes since there is no way they can be extended further.
There are complex rules regarding calling type, virtual/nonvirtual, and I don't know them all so I can't really outline them for you, but ...