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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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Java regex email
First of all, I know that using regex for email is not recommended but I gotta test this out.
20 Answers
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How to set -source 1.7 in Android Studio and Gradle
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This is essentially the same as the accepted answer.
– Kerem
Aug 12 '15 at 12:20
1
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In pure functional languages, is there an algorithm to get the inverse function?
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In some cases, yes! There's a beautiful paper called Bidirectionalization for Free! which discusses a few cases -- when your function is sufficiently polymorphic -- where it is possible, completely automatically to derive an inverse function. (It also discusses what makes...
Django: multiple models in one template using forms [closed]
...eparate project) OR creating a new Customer, then creating a Ticket and finally creating a Note assigned to the new ticket.
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How can I convert a series of images to a PDF from the command line on linux? [closed]
...rver I wrote in cgi/bash and want to be able to convert a bunch of images (all in one folder) to a pdf from the command line. How can that be done?
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Paste multiple columns together
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@baptiste ..possible without do.call?
– Anthony Damico
Jan 28 '13 at 23:11
1
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理解Python的 with 语句 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...hat the statement after with has to evaluate an object that responds to an __enter__() as well as an __exit__() function.
这看起来充满魔法，但不仅仅是魔法，Python对with的处理还很聪明。基本思想是with所求值的对象必须有一个__enter__()方法，一个__exit__()...
How to convert list of tuples to multiple lists?
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xs, ys = [x for x, y in zs], [y for x, y in zs]
return xs, ys
if __name__ == '__main__':
from timeit import timeit
setup_string='''\
N = 2000000
xs = list(range(1, N))
ys = list(range(N+1, N*2))
zs = list(zip(xs, ys))
from __main__ import t1, t2, t3
'''
print(f'zip:\t\t{timeit(...
UICollectionView current visible cell index
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The method [collectionView visibleCells] give you all visibleCells array you want. Use it when you want to get
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
for (UICollectionViewCell *cell in [self.mainImageCollection visibleCells]) {
NSIndexP...