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Is there a simple, elegant way to define singletons? [duplicate]
...he Metaclass approach.
class Singleton(type):
def __init__(cls, name, bases, dict):
super(Singleton, cls).__init__(name, bases, dict)
cls.instance = None
def __call__(cls,*args,**kw):
if cls.instance is None:
cls.instance = super(Singleton, cls).__call_...
How do I use IValidatableObject?
...in your table (such as the user who created it). It is required in the database but you step in in the SaveChanges in the context to populate it (eliminating the need for developers to remember to set it explicitly). You would, of course, validate before saving. So you don't mark the "creator" colum...
Node.js check if path is file or directory
...path alone is a file or directory.
The answer is to identify directory-based paths using "/." like --> "/c/dos/run/." <-- trailing period.
Like a path of a directory or file that has not been written yet. Or a path from a different computer. Or a path where both a file and directory of t...
tcp加速技术解决方案 - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...多通道和内存条rank级并行优化。一个内存通道一般使用64位数据总线，双通道同时工作提供了128位传输能力。Rank是指DIMM上几个内存颗粒共同提供的64位数据，同一条内存上的不同rank因为共享数据总线而不能被同时访问，但内存...
Among $_REQUEST, $_GET and $_POST which one is the fastest?
...les are in one superglobal). I actually rebuild $_REQUEST before using it based on the other superglobals because of 'variables_order'. I process $_COOKIE, then $_GET, then $_POST. That way POST vars have the highest priority and cookie vars get the lowest, which allows me to implicitly fix a num...
Convert Django Model object to dict with all of the fields intact
...e': <OtherModel: OtherModel object>,
'_state': <django.db.models.base.ModelState at 0x7ff0993f6908>,
'auto_now_add': datetime.datetime(2018, 12, 20, 21, 34, 29, 494827, tzinfo=<UTC>),
'foreign_key_id': 2,
'id': 1,
'normal_value': 1,
'readonly_value': 2}
This is by far the s...
List goals/targets in GNU make that contain variables in their definition
...
Can you parse the output from make -pn (i.e. make --print-data-base --dry-run)? It prints out all the variables, rules, implicit rules and which commands will be run in laborious detail.
share
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...
Polymorphism in C++
...<typename T>
void f(T& x) { x += 2; }
Virtual dispatch:
struct Base { virtual Base& operator+=(int) = 0; };
struct X : Base
{
X(int n) : n_(n) { }
X& operator+=(int n) { n_ += n; return *this; }
int n_;
};
struct Y : Base
{
Y(double n) : n_(n) { }
Y& ope...
Avoid trailing zeroes in printf()
...ly work out the field widths, then format the number using a format string based on that. The test harness main() shows this in action:
40.00000000000000000000 -> 40.000
359.01335000000000263753 -> 359.013
-359.00999000000001615263 -> -359.010
359.00999999999999090505 -> 359.010
...
How to get the screen width and height in iOS?
...
You might want to base the macro on AnswerBot's answer since that seems like the best answer.
– griotspeak
Aug 8 '13 at 13:17
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