To singleton or not to singleton, that is the question....

[JonB]

@JoeCFD ...which is why we don't risk using using... ;-)

[SimonSchroeder]

I agree that in general you should avoid using (for namespaces; now also allowed as a replacement for typedef).

There are, however, a few select places where I do use it for namespaces: 1) When using swap the preferred method is to using std::swap; (technically not a namespace) and then call swap unqualified (without a namespace, class name, etc). 2) For using string ""s and string view ""sv literals. Haven't used std::chrono much, but most likely would import the suffixes as well.

[SimonSchroeder]

@JoeCFD said in To singleton or not to singleton, that is the question....:

Calling baz() with using "using Foo;" can cause confusing while two namespaces are present at the same place.

In the concrete example you have given, it would not compile because the compiler cannot resolve the overload (i.e. Foo1::baz or Foo2::baz). You'd still need to use a fully qualified name. It only gets confusing when you have Foo1::baz(int) and Foo2::baz(double). You might write baz(1); when you actually want to call Foo2::baz. The software might even do the right thing for years. Someone might just introduce Foo1::baz years down the line and suddenly the behavior changes.