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is_null($x) vs $x === null in PHP [duplicate]
...someone strongly suggested that I use is_null() instead as it is specifically designed for the null-evaluation purpose. He also started talking about math or something.
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Get the name of the currently executing method
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Even better than my first answer you can use __method__:
class Foo
def test_method
__method__
end
end
This returns a symbol – for example, :test_method. To return the method name as a string, call __method__.to_s instead.
Note: This requires Ruby 1.8.7.
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What is function overloading and overriding in php?
...using the magic method __call.
An example of overriding:
<?php
class Foo {
function myFoo() {
return "Foo";
}
}
class Bar extends Foo {
function myFoo() {
return "Bar";
}
}
$foo = new Foo;
$bar = new Bar;
echo($foo->myFoo()); //"Foo"
echo($bar->myFoo()); //"Bar"...
How do I perform a Perl substitution on a string while keeping the original?
...a string without changing the original:
(my $newstring = $oldstring) =~ s/foo/bar/g;
In perl 5.14.0 or later, you can use the new /r non-destructive substitution modifier:
my $newstring = $oldstring =~ s/foo/bar/gr;
Note: The above solutions work without g too. They also work with any other...
Creating a singleton in Python
...mple implementation:
class Singleton(type):
_instances = {}
def __call__(cls, *args, **kwargs):
if cls not in cls._instances:
cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
return cls._instances[cls]
class Logger(object):
__meta...
Determine the type of an object?
...object, and isinstance() to check an object’s type against something. Usually, you want to use isistance() most of the times since it is very robust and also supports type inheritance.
To get the actual type of an object, you use the built-in type() function. Passing an object as the only param...
Adding 'serial' to existing column in Postgres
I have a small table (~30 rows) in my Postgres 9.0 database with an integer ID field (the primary key) which currently contains unique sequential integers starting at 1, but which was not created using the 'serial' keyword.
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间歇训练：参考Keep的原生应用案例 · App Inventor 2 中文网
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7 项通过
🧩 原生实现与数据
开始建立截止时间，每次 Clock 触发按真实时间重算剩余。暂停保存剩余毫秒，取消不计完成...
super() raises “TypeError: must be type, not classobj” for new-style class
...pe(OldStyle()) is the instance type, which does inherit from object. Basically, an old-style class just creates objects of type instance (whereas a new-style class creates objects whose type is the class itself). This is probably why the instance OldStyle() is an object: its type() inherits from ob...
How to perform Callbacks in Objective-C
...ust meant, in you're .m file. You'd have a separate class, let's call it "Foo". Foo would have a "MyClass *myClass" variable, and at some point Foo would say "[myClass setDelegate:self]". At any point after that, if anyone including foo invoked the doSomethingMethod on that instance of MyClass, foo...