[Interest] Are slots even needed these days?

[charleyb123 .]

> Since in modern Qt you connect signals to functions/lambdas, is there a
reason to declare slots anymore?

Interesting question, I've thought about this also.

IMHO, deep consideration is important:

  "slot":  A "slot" is a non-coupling thread-safe execution bridge.

It's already been mentioned in this thread:

Current Qt slots provide (beyond lambdas):

(1) Queued connections
(2) Runtime-reflected connections
(3) Uncoupled connections

Current slot implementation bridges runtime-reflection capabilities
(provided by QMetaObject), and provides the thread-safe event queue that
bridges "slot-execution" to occur on the "target-thread" for which the
"target-QObject" has "affinity".  Lambdas alone cannot do this -- some kid
of "event-queue" would be required that is "thread-aware" (yes, could be
provided through a library of some kind, that happens to be what Qt is
doing).

Because Qt slots can rely upon runtime type-reflection (provided by
QMetaObject), we can also couple signal/slot across two objects where the
code does not include both headers.  This is sometimes important to enable
designs for an "uncoupled-bridge" across components that cannot be coupled.

However, I agree that for the "common-case" (perhaps 80% of the time for
"typical" designs?) that lambdas are just-plain-awesome.

--charley
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