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What is the curiously recurring template pattern (CRTP)?
...e polymorphism. Here's a very simple example. In the below example, ProcessFoo() is working with Base class interface and Base::Foo invokes the derived object's foo() method, which is what you aim to do with virtual methods.
http://coliru.stacked-crooked.com/a/2d27f1e09d567d0e
template <typenam...
Cannot pass null argument when using type hinting
...ou can explicitly declare a variable to be null with this syntax
function foo(?Type $t) {
}
this will result in
$this->foo(new Type()); // ok
$this->foo(null); // ok
$this->foo(); // error
So, if you want an optional argument you can follow the convention Type $t = null whereas if you...
Can someone explain __all__ in Python?
...> import * is used on the module.
For example, the following code in a foo.py explicitly exports the symbols bar and baz:
__all__ = ['bar', 'baz']
waz = 5
bar = 10
def baz(): return 'baz'
These symbols can then be imported like so:
from foo import *
print(bar)
print(baz)
# The following w...
Local dependency in package.json
... npm. Example:
{
"name": "baz",
"dependencies": {
"bar": "file:../foo/bar"
}
}
Any of the following paths are also valid:
../foo/bar
~/foo/bar
./foo/bar
/foo/bar
The local package will be copied to the prefix (./node-modules).
npm < 2.0.0
Put somelocallib as dependency in your p...
Rails where condition using NOT NIL
...
The canonical way to do this with Rails 3:
Foo.includes(:bar).where("bars.id IS NOT NULL")
ActiveRecord 4.0 and above adds where.not so you can do this:
Foo.includes(:bar).where.not('bars.id' => nil)
Foo.includes(:bar).where.not(bars: { id: nil })
When working...
How do I return the response from an asynchronous call?
I have a function foo which makes an asynchronous request. How can I return the response/result from foo ?
39 Answers
...
Get top n records for each group of grouped results
...s can be returned, as shown below:
.headers on
.mode column
CREATE TABLE foo (person, groupname, age);
INSERT INTO foo VALUES('Paul',2,36);
INSERT INTO foo VALUES('Laura',2,39);
INSERT INTO foo VALUES('Joe',2,36);
INSERT INTO foo VALUES('Bob',1,32);
INSERT INTO foo VALUES('Jill',1,34);
INSERT INTO...
ReadOnlyCollection or IEnumerable for exposing member collections?
...pe to be an immutable collection, and then expose that directly - assuming Foo itself is immutable, of course.
Updated answer to address the question more directly
Is there any reason to expose an internal collection as a ReadOnlyCollection rather than an IEnumerable if the calling code only it...
How to call a Parent Class's method from Child Class in Python?
...
Yes, but only with new-style classes. Use the super() function:
class Foo(Bar):
def baz(self, arg):
return super().baz(arg)
For python < 3, use:
class Foo(Bar):
def baz(self, arg):
return super(Foo, self).baz(arg)
...
How do you normalize a file path in Bash?
I want to transform /foo/bar/.. to /foo
22 Answers
22
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