C++ With Initializer List a thing, when to use normal constructor?

Question

I just started getting back into C++ here recently and learned about Initializer Lists. It seems to be the standard way to initialize members. That being said I have 2 quest

Answer 1

You should know that "setting (member data) in the constructor (body)" is assignment to an already-initialized object. That cannot supply constructor arguments. const members and references cannot be assigned.

The ctor-initializer-list (and since C++11, brace-or-equal-initializers specified at the member point of declaration) do true initialization, and should be preferred.

The constructor body can still have some uses... doing things with side effects, or looping... but even these can be accomplished by invoking a helper function from inside one of the ctor-initializer-list expressions.

Also, member initialization is the only way for their setup to fail in a way that doesn't lead to later destruction. An exception in a constructor body will abort creation of the parent object... but destructors still need to run for all subobjects, so any setup to put them in a known, destructable state has to already be complete.