Convenient C++ struct initialisation

Question

I\'m trying to find a convenient way to initialise \'pod\' C++ structs. Now, consider the following struct:

struct FooBar {
  int foo;
  float bar;
};
// jus         


        

Answer 1

Your question is somewhat difficult because even the function:

static FooBar MakeFooBar(int foo, float bar);

may be called as:

FooBar fb = MakeFooBar(3.4, 5);

because of the promotion and conversions rules for built-in numeric types. (C has never been really strongly typed)

In C++, what you want is achievable, though with the help of templates and static assertions:

template 
FooBar MakeFooBar(Integer foo, Real bar) {
  static_assert(std::is_same::value, "foo should be of type int");
  static_assert(std::is_same::value, "bar should be of type float");
  return { foo, bar };
}

In C, you may name the parameters, but you'll never get further.

On the other hand, if all you want is named parameters, then you write a lot of cumbersome code:

struct FooBarMaker {
  FooBarMaker(int f): _f(f) {}
  FooBar Bar(float b) const { return FooBar(_f, b); }
  int _f;
};

static FooBarMaker Foo(int f) { return FooBarMaker(f); }

// Usage
FooBar fb = Foo(5).Bar(3.4);

And you can pepper in type promotion protection if you like.