C++ friend inheritance?
Friendship is not inherited in C++. The standard says (ISO/IEC 14882:2003, section 11.4.8): Friendship is neither inherited nor transitive.
subclass
What is the difference between parent and base in Perl 5?
base tried to do one too many things – automatically handling loading modules but also allowing establishing inheritance from classes already loaded (possibly from a file whose name wasn’t based on the module name). To sort of make it work, there was some hackery that caused surprising results in some cases. Rather than break backwards … Read more
Subclassing Python dictionary to override __setitem__
I’m answering my own question, since I eventually decided that I really do want to subclass Dict, rather than creating a new mapping class, and UserDict still defers to the underlying Dict object in some cases, rather than using the provided __setitem__. After reading and re-reading the Python 2.6.4 source (mostly Objects/dictobject.c, but I grepped … Read more
Subclass dict: UserDict, dict or ABC?
If you want a custom collection that actually holds the data, subclass dict. This is especially useful if you want to extend the interface (e.g., add methods). None of the built-in methods will call your custom __getitem__ / __setitem__, though. If you need total control over these, create a custom class that implements the collections.MutableMapping … Read more
Swift + CoreData: Cannot Automatically Set Optional Attribute On Generated NSManagedObject Subclass
The optional checkbox in the Core Data Model Editor has been existing before Swift and its optionals where introduced. Apple states about it in its Core Data Programming Guide: You can specify that an attribute is optional — that is, it is not required to have a value. In general, however, you are discouraged from … Read more
Why doesn’t a using-declaration work to solve the diamond problem?
Someone else can find the standard quote but I’m going to explain conceptually. It doesn’t work because a using-declaration only affects name lookup. Your using-declaration causes name lookup to succeed where it would otherwise fail, that is, it tells the compiler where to find the function f. But it does not tell it which A … Read more
Reclassing an instance in Python
Reclassing instances like this is done in Mercurial (a distributed revision control system) when extensions (plugins) want to change the object that represent the local repository. The object is called repo and is initially a localrepo instance. It is passed to each extension in turn and, when needed, extensions will define a new class which … Read more
Subclassing tuple with multiple __init__ arguments
Because tuples are immutable, you have to override __new__ instead: python docs object.__new__(cls[, …]) Called to create a new instance of class cls. __new__() is a static method (special-cased so you need not declare it as such) that takes the class of which an instance was requested as its first argument. The remaining arguments are … Read more
Subclassing int in Python
int is immutable so you can’t modify it after it is created, use __new__ instead class TestClass(int): def __new__(cls, *args, **kwargs): return super(TestClass, cls).__new__(cls, 5) print TestClass()
Add rounded corners to all UIImageViews
Check this – Rounded Corners on UIImage The layer modification seems to be the best way. UIImageView * roundedView = [[UIImageView alloc] initWithImage: [UIImage imageNamed:@”wood.jpg”]]; // Get the Layer of any view CALayer * l = [roundedView layer]; [l setMasksToBounds:YES]; [l setCornerRadius:10.0];