Object literal alternative in C++

Question

I'm coming from Javascript like language where I can make functions like this.

function tween(obj, tweenParams, time, tweenOptions);

This is used like:

tween(mySprite, {x: 10, y: 10}, 1, {startDelay: 1, loops: 5});

If it's not clear, this lerps mySprite's x and y property to 10 over the course of 1 second, looping 5 times with a 1 second delay. tweenParams can contain any values that the obj might have, and tweenOptions is a fixed struct.

I want to know how terse this can reasonable be in C++, struct and array initializes don't seem flexible enough to express this. My best guess involves calling multiple tween functions one property at a time, something like.

TweenOptions opts = {};
opts.startDelay = 1;
opts.loops = 5;
tween(&mySprite.x, 10, 1, opts);
tween(&mySprite.y, 10, 1, opts);

I don't know much about C++ advanced features, maybe operator overloading or custom initializes could help me here?

EDIT: To be clear, I don't expect it to exactly match the Javascript example, I just want to know how terse this can reasonably be.

Answer 1

Current versions of C++ do not allow this syntax. However, one of the proposals which according to this post was adopted for C++20, will make it possible by using designated initializers (if, of course it will make it there).

The proposal, available here, borrows C99 syntax of nominating members when using aggregate initialization in C++ classes. Coupled together with C++11 feature of uniform initializaion, it will allow for very similar syntax to the one you are asking.

For example,

struct args {
    int x;
    int y;
};

void foo(args a);
...
foo({.x = 10, .y = 25});