subclassing

I want to create a text display area (either UILabel or UITextView) in my iPhone app which (1) allows scrolling and (2) does not allow selection. I have tried the following techniques unsuccessfully: Basic UILabel: Didn't allow scrolling, and clipped text to the bottom of UILabel space on screen. Giant UILabel within a UIScrollView: the UILabel kept placing the text (vertically) at the center of the giant UILabel, so it often was outside of my UIScrollView. UITextView: So far this approach has worked the best, because it scrolls and does not clip the text. I can even subclass UITextView to

I have two class, TNode and TMaster. I subclassing TMaster from TNode. The goal is to create a TMaster instance that contains all the data of a previously created TNode instance. Is there any 'built-in' method to achieve this, or it should be done manually? type Tnode = class(TObject) private FSite: TSite; FhndNode: THandle; FnodeID: word; FslaveID: longword; FcoordX: double; FcoordY: double; FhndSubRect: THandle; FdNodes: TdNodes; Fdestinations: Tdestinations; FGroup: byte; FDomain: byte; FRFsense: byte; FComm: byte; FlcIDtextHnd: THandle; ... public constructor create(); ... end; TMaster =

Goal: Creating an item delegate with custom textual content to be used in QListView . Problem: Drawing text with QPainter in a reimplementation of the paint() method of a QAbstractItemDelegate 's subclass is noticably slower than drawing shapes and pixmaps. Changing the base class to QStyledItemDelegate does not improve the speed. Setup: Qt 5.9.1, MSVC 2017, tested on Windows 7/10 Pre-research: A similar bug is reported here , however in this particular case the performance issue exists even if QPainter::setFont() is not used. The Qt examples on item delegates do not help much, as they show

Why isn't this valid C++?: enum foo : unsigned { first_foo, second_foo }; enum bar : foo { best_foo = first_foo }; GCC 5.4.0 says: /tmp/a.cpp:3:16: error: underlying type ‘foo’ of ‘bar’ must be an integral type enum bar : foo { best_foo = first_foo }; I can understand why I would get this error if foo were a float , or some struct, or what-not. But this seems perfectly legit to me in terms of semantics, type safety etc. What am I missing? When you add things to C++, you tend to add the minimium amount that solves a problem. The enum A:int syntax lets you specify exactly how the enum A is

# Python 3 class Point(tuple): def __init__(self, x, y): super().__init__((x, y)) Point(2, 3) would result in TypeError: tuple() takes at most 1 argument (2 given) Why? What should I do instead? tuple is an immutable type. It's already created and immutable before __init__ is even called. That is why this doesn't work. If you really want to subclass a tuple, use __new__ . >>> class MyTuple(tuple): ... def __new__(typ, itr): ... seq = [int(x) for x in itr] ... return tuple.__new__(typ, seq) ... >>> t = MyTuple((1, 2, 3)) >>> t (1, 2, 3) 来源： https://stackoverflow.com/questions/4827303/problem

As we all know, there are multiple reasons of OutOfMEmoryError (see first answer ). Why there is only one exception covering all these cases instead of multiple fine-grained ones inheriting from OutOfMEmoryError ? I'd expect because you really can't do anything else when that happens: it almost doesn't matter WHY you ran out, since you're screwed regardless. Perhaps the additional info would be nice, but... I know tomcat tries to do this "Out Of Memory Parachute" thing, where they hold onto a chunk of memory and try and release it, but I'm not sure how well it works. The garbage collection