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When should I use the Visitor Design Pattern? [closed]
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(Suppose it is a complex hierarchy with a well-established interface.)
Now we want to add a new operation to the hierarchy, namely we want each animal to make its sound. As far as the hierarchy is this simple, you can do it with straight polymorphism:
class Animal
{ public: virtual void makeSou...
performSelector may cause a leak because its selector is unknown
...e (the (void *) on the right hand side simply tells the compiler that you know what you're doing and not to generate a warning since the pointer types don't match).
Finally, you call the function pointer2.
Complex Example
When the selector takes arguments or returns a value, you'll have to change...
Remove last character from string. Swift language
...oIndex. Also, as of Xcode 7, string no longer has a .count property, it is now only applied to characters: string.characters.count
– kakubei
Jul 22 '15 at 15:18
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Iterating through a JSON object
...nt:
from __future__ import print_function
for song in json_object:
# now song is a dictionary
for attribute, value in song.items():
print(attribute, value) # example usage
NB: You could use song.iteritems instead of song.items if in Python 2.
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Re-raise exception with a different type and message, preserving existing information
...ture, the __cause__ attribute is set. The built-in exception handler also knows how to report the exception's “cause” and “context” along with the traceback.
In Python 2, it appears this use case has no good answer (as described by Ian Bicking and Ned Batchelder). Bummer.
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Parse a .py file, read the AST, modify it, then write back the modified source code
...asy, without writing new .py files! If you expand your question to let us know what you actually want to accomplish, new .py files will probably not be involved in the answer at all; I have seen hundreds of Python projects doing hundreds of real-world things, and not a single one of them needed to e...
How to set versionName in APK filename using gradle?
... Is there any way to add variant.buildType.name to the name? I know this isn't really default config related, but I'm trying to figure out how to remove the obsolete variantOutput.getAssemble() warning
– Allan W
Mar 5 '19 at 5:51
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How do I print the elements of a C++ vector in GDB?
...db wiki page particularly readable, maybe because it's "slightly" outdated now? For instance, I had the impression that the suggested content of the $HOME/.gdbinit was necessary. At the moment I end up with no such file at all and gdb correctly showing the content of std::vector. However, since duri...
Python strftime - date without leading 0?
...>>> '{dt.year}/{dt.month}/{dt.day}'.format(dt = datetime.datetime.now())
'2013/4/19'
Though perhaps beyond the scope of the original question, for more interesting formats, you can do stuff like:
>>> '{dt:%A} {dt:%B} {dt.day}, {dt.year}'.format(dt=datetime.datetime.now())
'Wedne...
How do I use IValidatableObject?
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The problem with this solution is that now you depend on the caller for your object to be properly validated.
– cocogza
Feb 28 '17 at 22:06
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