How to query mongodb with DBRef
Got it: db.post.find({‘author.$id’: ‘foo’})
reference
Cannot borrow as mutable because it is also borrowed as immutable
A MRE of your problem can be reduced to this: // This applies to the version of Rust this question // was asked about; see below for updated examples. fn main() { let mut items = vec![1]; let item = items.last(); items.push(2); } error[E0502]: cannot borrow `items` as mutable because it is also borrowed as … Read more
How do I implement the Add trait for a reference to a struct?
You need to implement Add on &Vector rather than on Vector. impl<‘a, ‘b> Add<&’b Vector> for &’a Vector { type Output = Vector; fn add(self, other: &’b Vector) -> Vector { Vector { x: self.x + other.x, y: self.y + other.y, } } } In its definition, Add::add always takes self by value. But references … Read more
Get value from the cell above
You can address it like this: =INDIRECT(ADDRESS(ROW()-1,COLUMN())) COLUMN() returns a numeric reference to the current column ROW() returns a numeric reference to the current row. In the example here, subtracting 1 from the row gives you the previous row. This math can be applied to the ROW() and/or the COLUMN(), but in answering your question, … Read more
Is there any way to return a reference to a variable created in a function?
The question you asked TL;DR: No, you cannot return a reference to a variable that is owned by a function. This applies if you created the variable or if you took ownership of the variable as a function argument. Solutions Instead of trying to return a reference, return an owned object. String instead of &str, … Read more
Cannot move out of borrowed content / cannot move out of behind a shared reference
Let’s look at the signature for into_bytes: fn into_bytes(self) -> Vec<u8> This takes self, not a reference to self (&self). That means that self will be consumed and won’t be available after the call. In its place, you get a Vec<u8>. The prefix into_ is a common way of denoting methods like this. I don’t … Read more
Why are explicit lifetimes needed in Rust?
The other answers all have salient points (fjh’s concrete example where an explicit lifetime is needed), but are missing one key thing: why are explicit lifetimes needed when the compiler will tell you you’ve got them wrong? This is actually the same question as “why are explicit types needed when the compiler can infer them”. … Read more