self

I am making a constructor in Python. When called with an existing object as its input, it should set the "new" object to that same object. Here is a 10 line demonstration: class A: def __init__(self, value): if isinstance(value, A): self = value else: self.attribute = value a = A(1) b = A(a)#a and b should be references to the same object print("b is a", b is a)#this should be true: the identities should be the same print("b == a", b == a)#this should be true: the values should be the same I want the object A(a) constructed from the existing object a to be a . Why is it not? To be clear, I

I wrote an extension onto Int as below. extension Int { func squared () -> Int { return self * self } } print(10.squared()) // works The above code works. Now I want to extend the IntegerType protocol so that Int, UInt, Int64, etc would all conform. My code is as below. extension IntegerType { func squared () -> IntegerType { // this line creates error return self * self } } I get error: Protocol 'IntegerType' can only be used as a generic constraint because it has Self or associated type requirements I already saw this question and its video & this question, still couldn't understand. I only

Can I write a function that returns iteself? I was reading some description on closures - see Example 6 - where a function was returning a function, so you could call func()(); as valid JavaScript. So I was wondering could a function return itself in such a way that you could chain it to itself indefinitely like this: func(arg)(other_arg)()(blah); Using arguments object, callee or caller? There are 2-3 ways. One is, as you say, is to use arguments.callee . It might be the only way if you're dealing with an anonymous function that's not stored assigned to a variable somewhere (that you know of)

Quick question regarding the use of "SELF" inside a module or library. Basically what is the scope/context of "SELF" as it pertains to a module or library and how is it to be properly used? For an example of what I'm talking about, check out the "AuthenticatedSystem" module installed with "restful_authentication". NOTE: I'm aware that 'self' equates to 'this' in other languages and how 'self' operates on a class/object, however in the context of a module/library there is nothing to 'self'. So then what is the context of self inside something like a module where there is no class? In a module:

I've got a WPF Window , and somewhere there is a ListView where I bind a List<string> to. Now somewhere in my ListView there is a TextBox and the Content property is set to {Binding} . But this is the shorthand. How do I write the full binding to bind to itself? {Binding Path=Self} doesn't work, neither does {Binding Self} (where the latter is a shortcut for the former). Short answer : {Binding} is not a shortcut for "binding to itself" (in the sense of RelativeSource.Self ). Rather, {Binding} is equivalent to {Binding Path=.} , which binds to the current source. To elaborate : A binding has a

Question: when do I need to use self in my models in Rails? I have a set method in one of my models. class SomeData < ActiveRecord::Base def set_active_flag(val) self.active_flag = val self.save! end end When I do this, everything works fine. However, when I do this: class SomeData < ActiveRecord::Base def set_active_flag(val) active_flag = val save! end end The active_flag value doesn't change, rather it fails silently. Can someone explain? I can't find any duplicates, but if someone finds one that's fine too. DVG When you're doing an action on the instance that's calling the method, you use

Yet another question on what the 'self' is for, what happens if you don't use 'self' and what's 'cls' for. I "have done my homework", I just want to make sure I got it all. self - To access an attribute of an object, you need to prefix the attribute name with the object name ( objname.attributename ). The same way self is used to access an attribute inside the object (class) itself. So if you didn't prefix a variable with self in a class method, you wouldn't be able to access that variable in other methods of the class, or outside of the class. So you could omit it if you wanted to make the