instance-variables

问题 I am a little bit confused about the following piece of code: public class Test{ int x = giveH(); int h = 29; public int giveH(){ return h; } public static void main(String args[]) { Test t = new Test(); System.out.print(t.x + " "); System.out.print(t.h); } } The output here is 0 29 , but I thought that this has to be a compiler error, because the variable h should have not been initialized when it comes to the method giveH() . So, does the compilation go through the lines from top to bottom?

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: How does an underscore in front of a variable in a cocoa objective-c class work? I'm using the same convention for instance variable and properties naming as shown by sebnow in his following answer: instance variable/ method argument naming in Objective C I copy paste his example code here: @interface Foo : NSObject { id _bar; } @property (nonatomic, retain) id bar; - (id) initWithBar:(id)aBar; @end

问题 I now (or so I have read) that it is not possible in Python 2.x, and can't find it for Python 3 either, but maybe I don't know how to search for it... It easier to explain it with a simple Python example: for i in range(11): one_turtle.penup() one_turtle.forward(50) one_turtle.down() one_turtle.forward(8) one_turtle.up() one_turtle.forward(8) one_turtle.stamp() one_turtle.forward(-66) one_turtle.left(360/12) I'd like to avoid repeating "one_turtle" the same way you can do in VBA, which it

问题 I now (or so I have read) that it is not possible in Python 2.x, and can't find it for Python 3 either, but maybe I don't know how to search for it... It easier to explain it with a simple Python example: for i in range(11): one_turtle.penup() one_turtle.forward(50) one_turtle.down() one_turtle.forward(8) one_turtle.up() one_turtle.forward(8) one_turtle.stamp() one_turtle.forward(-66) one_turtle.left(360/12) I'd like to avoid repeating "one_turtle" the same way you can do in VBA, which it

问题 This question already has answers here : How to avoid having class data shared among instances? (7 answers) Closed 3 years ago . I don't understand the difference in the following example. One time an instance of a class can CHANGE the class variable of another instance and the other time it can't? Example 1: class MyClass(object): mylist = [] def add(self): self.mylist.append(1) x = MyClass() y = MyClass() x.add() print "x's mylist: ",x.mylist print "y's mylist: ",y.mylist Output: x's mylist

问题 I've seen code examples (from the book Beginning iPhone 4 Development) where they both declare ivars inside the interface block and then declare properties for the same. Like this: @interface ViewController : UIViewController { UITableView *table; } @property (nonatomic, retain) IBOutlet UITableView *table; What would be the purpose/benefit of this? As I understand that with the modern runtime version (iPhone and 64-bit OS X applications) you only need to declare properties and can leave out

问题 I'm having a hard time understanding why I need to declare Instance Variables. Let me explain what I mean.. for example.. @interface LearningViewController : UIViewController { UILabel *myText; // <--- Instance Variables } @property (nonatomic,retain) IBOutlet UILabel *myText; -(IBAction)method:(id)sender; @end this can also be done as @interface LearningViewController : UIViewController { //instance variables go here, but are not declared, I just leave this field blank } @property (nonatomic

问题 I have a subclass of PFObject called Attendee . In this class, there is a instance variable I have called isFavorite . Below is its class definition: @NSManaged var isFavorite: Bool This is an instance var that is local to the device and I never sync it up to the server. In addition, I never explicitly instantiate the Attendee class, but rather create it by typecasting from PFObject . I would like to set the above var to have an initial value of false . How would I achieve this? 回答1: var

问题 This question already has an answer here : Best way of declaring private variables in cocoa (1 answer) Closed 6 years ago . Having ARC enabled for an iOS app, if I want a class to have a private value/object, it should be better to declare this: // .m file @interface MyClass () @property (strong, nonatomic) NSString *name; @end or this?: @implementation MyClass { NSString *name; } What memory management considerations should I have? Thanks! 回答1: You can use either approach. In the first case

问题 I'm trying to initialize and instance variable as an array as follows: class Arch < ActiveRecord::Base attr_accessor :name1 def initialize @name1 = [] end def add_name1(t) @name1 << t end end When I try Arch.new in a console session I get (Object doesn't support #inspect). What's up? How do I make an instance array variable? I tried to follow this like so: class Arch < ActiveRecord::Base attr_accessor :name1 def after_initialize @name1 = [] end def add_name1(t) @name1 << t end end and my