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Simplest/Cleanest way to implement singleton in JavaScript?
... pattern:
short form
var Foo = function () {
"use strict";
if (Foo._instance) {
//this allows the constructor to be called multiple times
//and refer to the same instance. Another option is to
//throw an error.
return Foo._instance;
}
Foo._instance = t...
How to get current timestamp in milliseconds since 1970 just the way Java gets
...chrono>
// ...
using namespace std::chrono;
milliseconds ms = duration_cast< milliseconds >(
system_clock::now().time_since_epoch()
);
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...
When to use NSInteger vs. int
...amic typedef*s to one of these types, and they are defined like this:
#if __LP64__ || TARGET_OS_EMBEDDED || TARGET_OS_IPHONE || TARGET_OS_WIN32 || NS_BUILD_32_LIKE_64
typedef long NSInteger;
typedef unsigned long NSUInteger;
#else
typedef int NSInteger;
typedef unsigned int NSUInteger;
#endif
Wit...
How to check if a variable is a dictionary in Python?
...t, defaultdict, or Counter from the collections module:
if isinstance(any_object, dict):
But there are even more flexible options.
Supporting abstractions:
from collections.abc import Mapping
if isinstance(any_object, Mapping):
This allows the user of your code to use their own custom implem...
Underscore prefix for property and method names in JavaScript
...d variable to be private was accepted. Chrome 74 ships with this support.
_ prefixed variable names are considered private by convention but are still public.
This syntax tries to be both terse and intuitive, although it's rather different from other programming languages.
Why was the sig...
How to rename with prefix/suffix?
...ly be short and simple for this. For example, to rename all *.jpg to prefix_*.jpg in the current directory:
for filename in *.jpg; do mv "$filename" "prefix_$filename"; done;
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Why rename synthesized properties in iOS with leading underscores? [duplicate]
...ariables had to be instantiated explicitly:
@interface Foo : Bar {
Baz *_qux;
}
@property (retain) Baz *qux;
@end
@implementation Foo
@synthesize qux = _qux;
- (void)dealloc {
[_qux release];
[super dealloc];
}
@end
People would prefix their instance variables to differentiate them from...
How do I partially update an object in MongoDB so the new object will overlay / merge with the exist
...e data then?
You know you can do the following:
db.collection.update( { _id:...} , { $set: someObjectWithNewData }
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How can I use UUIDs in SQLAlchemy?
... is an example:
from sqlalchemy.dialects.postgresql import UUID
from flask_sqlalchemy import SQLAlchemy
import uuid
db = SQLAlchemy()
class Foo(db.Model):
# id = db.Column(db.Integer, primary_key=True)
id = db.Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4, unique=True, n...
Select the values of one property on all objects of an array in PowerShell
...
$objects | % Name # short for: $objects | ForEach-Object -Process { $_.Name }
For the sake of completeness: The little-known PSv4+ .ForEach() array method, more comprehensivel discussed in this article, is yet another alternative:
# By property name (string):
$objects.ForEach('Name')
# By s...