subclassing

问题 I would like to be able to thin the UITabBar's height by removing each item's titles and reclaiming the vertical space they take up, a la Tweetie 2. This doesn't seem settable in the .xib or programmatically. Will I have to subclass the UITabBar and roll my own? 回答1: Roll your own. I'm sure Tweetie 2's is custom; and the height is set in the handed down UITabBar. 回答2: You can achieve a similar effect by placing a segmented control inside a uitoolbar. I did this and it looks quite nice. 来源：

问题 I am trying to subclass str object, and add couple of methods to it. My main purpose is to learn how to do it. Where I am stuck is, am I supposed to subclass string in a metaclass, and create my class with that meta, or subclass str directly? And also, I guess I need to implement __new__() somehow, because, my custom methods will modify my string object, and will return new mystr obj. My class's methods, should be completely chainable with str methods, and should always return a new my class

问题 I am trying to subclass str object, and add couple of methods to it. My main purpose is to learn how to do it. Where I am stuck is, am I supposed to subclass string in a metaclass, and create my class with that meta, or subclass str directly? And also, I guess I need to implement __new__() somehow, because, my custom methods will modify my string object, and will return new mystr obj. My class's methods, should be completely chainable with str methods, and should always return a new my class

问题 This list shows what methods you need to implement for your class to be "regarded" as Sequence: __getitem__ , __len__ , __contains__ , __iter__ , __reversed__ , index , and count . So why does this minimal implementation does not work, i.e. why issubclass(S, Sequence) is False ? from collections import * class S(object): def __getitem__(self, item): raise IndexError def __len__(self): return 0 def __contains__(self, item): return False def __iter__(self): return iter(()) def __reversed__(self

问题 Is it possible to narrow the allowed type of an ivar in a subclass. Something like this: @interface person: NSObject { NSArray *friendArray; } @interface mutablePerson: person { NSMutableArray *friendArray; } I just tried that exact code, and Xcode gave me a compile error. I'm wondering if there is a way around it. The project I am working on is going to have a lot of this sort of situation. I understand that I can use casts to make the code work. But I will be making an awful lot of casts if

问题 I am subclassing UIView trying to load the view i have dropped in interface builder from a nib file. I get the following error on the return line: Terminating app due to uncaught exception 'NSGenericException', reason: 'This coder requires that replaced objects be returned from initWithCoder:' - (id)initWithCoder:(NSCoder *)aDecoder { [super initWithCoder:aDecoder]; NSArray *objects = [[NSBundle mainBundle] loadNibNamed:@"MyView" owner:nil options:nil]; if (self = [objects objectAtIndex:0]) {

问题 Whole sample project can be found here: Sample project Normal MDI child: MDI child is detached out of MDI client area: Problem is after MDI child is detached, I am not able to click on menu/controls anymore. I think one approach is to subclass winproc of MDI app, and then catching the messages and redirect them (like this one). But I dont know where to begin. Any idea/ other approaches are welcome! The code I used to detach MDI child: HWND MDIHwnd = pMainFrame->m_hWndMDIClient; HWND

问题 I have two models, Article and Recipe, which have a bunch of the same attributes and methods. I want to make the subclasses of a new class "Post" and move all their shared logic in there so I'm not maintaining duplicate code. I've tried this: class Recipe < Post; end class Article < Post; end class Post < ActiveRecord::Base #all the shared logic end All of these classes are in the standard ./app/models folder. This code, however, throws a ActiveRecord::StatementInvalid error when I go to

问题 So I would like to have a BaseEntity which contains common columns that appear in all tables and use inheritance to keep mapping of these fields in one place. For the sake of simplicity I will only include one field (Id). The code looks as follows: [Serializable] public abstract class BaseEntity { public Guid Id { get; set; } } public class Hedge : BaseEntity { public virtual DateTime HedgeDate { get; set; } public virtual DateTime SettleDate { get; set; } } public class Trade : BaseEntity {

问题 When working on essentially a custom enumerated type implementation, I ran into a situation where it appears I had to derive separate yet almost identical subclasses from both int and long since they're distinct classes in Python. This seems kind of ironic since instances of the two can usually be used interchangeably because for the most part they're just created automatically whenever required. What I have works fine, but in the spirit of DRY (Don't Repeat Yourself), I can't help but wonder