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The issue is that, in the function passed to reduce
, you’re adding each object directly to the accumulator rather than to its intended parent. These are the problem lines:
if (index == array.length - 1) {
accumulator[val] = value;
} else if (!accumulator.hasOwnProperty(val)) {
accumulator[val] = {}; // update the accumulator object
}
There’s no pretty way (that I can think of at least) to do what you want using methods like reduce
in vanilla JS, so I’d suggest using a for loop instead - especially if you’re new to programming. Something along these lines (not written to be actual code, just to give you an idea):
let curr = settings;
const split = url.split("/");
for (let i = 0; i < split.length: i++) {
const val = split[i];
if (i != split.length-1) {
//add a check to see if curr[val] exists
let next = {};
curr[val] = next;
curr = next;
}
//add else branch
}
It’s missing some things, but the important part is there - every time we move one level deeper in the URL, we update curr
so that we keep our place instead of always adding to the top level.
This is a use-after-free, which should be impossible in safe Rust due to the borrow checker. The only way for this to happen would be incorrect unsafe code (still possible, but dramatically reduced code surface to worry about) or a compiler bug. To allocate heap space in safe Rust, you have to use types provided by the language like
Box
,Rc
,Vec
, etc. To free that space (in Rust terminology, dropping it by usingdrop()
or letting it go out of scope) you must be the owner of it and there may be current borrows (i.e. no references may exist). Once the variable isdrop
ed, the variable is dead so accessing it is a compiler error, and the compiler/std handles freeing the memory.There’s some extra semantics to some of that but that’s pretty much it. These kind of memory bugs are basically Rust’s raison d’etre - it’s been carefully designed to make most memory bugs impossible without using
unsafe
. If you’d like more information I’d be happy to provide!