Helper methods for initialization: class MyStream(object): @classmethod def from_file(cls, filepath, ignore_comments=False): with open(filepath, ‘r’) as fileobj: for obj in cls(fileobj, ignore_comments): yield obj @classmethod def from_socket(cls, socket, ignore_comments=False): raise NotImplemented # Placeholder until implemented def __init__(self, iterable, ignore_comments=False): …
Sometimes texts have to be read more for the flavor of the idea rather than for the details. This is one of those cases. In the linked page, Examples 2.5, 2.6 and 2.7 should all use one method, do_your_stuff. (That is, do_something should be changed to do_your_stuff.) In addition, as Ned Deily pointed out, A.do_your_stuff … Read more
I think in Ruby 1.9 you can do this: class A define_singleton_method :loudly do |message| puts message.upcase end end A.loudly “my message” # >> MY MESSAGE
Your guess is correct – you understand how classmethods work. The why is that these methods can be called both on an instance OR on the class (in both cases, the class object will be passed as the first argument): class Dummy(object): @classmethod def some_function(cls,*args,**kwargs): print cls #both of these will have exactly the same … Read more
If you’re using a new-style class (i.e. derives from object in Python 2, or always in Python 3), you can do it with super() like this: super(Derived, cls).do(a) This is how you would invoke the code in the base class’s version of the method (i.e. print cls, a), from the derived class, with cls being … Read more
Read this for detail : // 1 define a function pointer and initialize to NULL int (TMyClass::*pt2ConstMember)(float, char, char) const = NULL; // C++ class TMyClass { public: int DoIt(float a, char b, char c){ cout << “TMyClass::DoIt”<< endl; return a+b+c;}; int DoMore(float a, char b, char c) const { cout << “TMyClass::DoMore” << endl; … Read more
Here’s how I would do this: class ClassPropertyDescriptor(object): def __init__(self, fget, fset=None): self.fget = fget self.fset = fset def __get__(self, obj, klass=None): if klass is None: klass = type(obj) return self.fget.__get__(obj, klass)() def __set__(self, obj, value): if not self.fset: raise AttributeError(“can’t set attribute”) type_ = type(obj) return self.fset.__get__(obj, type_)(value) def setter(self, func): if not isinstance(func, … Read more
Class methods are for when you need to have methods that aren’t specific to any particular instance, but still involve the class in some way. The most interesting thing about them is that they can be overridden by subclasses, something that’s simply not possible in Java’s static methods or Python’s module-level functions. If you have … Read more
Rather than referring to the literal name of the class, inside an instance method you can just call self.class.whatever. class Foo def self.some_class_method puts self end def some_instance_method self.class.some_class_method end end print “Class method: ” Foo.some_class_method print “Instance method: ” Foo.new.some_instance_method Outputs: Class method: Foo Instance method: Foo
Like most of the other answers have said, instance methods use an instance of a class, whereas a class method can be used with just the class name. In Objective-C they are defined thusly: @interface MyClass : NSObject + (void)aClassMethod; – (void)anInstanceMethod; @end They could then be used like so: [MyClass aClassMethod]; MyClass *object = … Read more