Question

I can do this on initialization for a struct Foo:

Foo foo =  {bunch, of, things, initialized};

but, I can’t do this:

Foo foo;
foo = {bunch, of, things, initialized};

So, two questions:

1. Why can’t I do the latter, is the former a special constructor for initialization only?

2. How can I do something similar to the second example, i.e. declare a bunch of variables for a struct in a single line of code after it’s already been initialized? I’m trying to avoid having to do this for large structs with many variables:

   Foo foo;
   
   foo.a = 1;
   foo.b = 2;
   foo.c = 3;
   //... ad infinitum
   

Answer 1

The first is an aggregate initializer – you can read up on those and tagged initializers at this solution:

What is tagged structure initialization syntax?

It is a special initialization syntax, and you can’t do something similar after initialization of your struct. What you can do is provide a member (or non-member) function to take your series of values as parameters which you then assign within the member function – that would allow you to accomplish this after the structure is initialized in a way that is equally concise (after you’ve written the function the first time of course!)