how can I specify the lifetimeof a fully contained struct in rust with no cicular deps

0
votes

I'm trying to create a struct that contains a list of other structs, (could be fixed size if that helped)

struct Container<'m> {
    contained: Vec<&'m Contained>,
}

struct Contained {
    id: u64,
}

impl Container<'_> {

    pub fn new<'m>() -> Container<'m> {
        Container {
            contained: Vec::new()
        }
    }

    pub fn new_contained<'m>(&mut self, id: u64) {
        let c = Contained {
            id
        };
        self.contained.push(&c);
                            ^^ lifetime of Contained ends here
    }
}

I can see that life time of Contained ends but I cant see how to create a struct with a given lifetime.

Do I have any alternatives I tried using a fixed size array instead of a Vec this way the Container owns the contents of the Array, but I cant create a zero sized array to start with.

1
rust
Why does your Vec contain references to Contained? Simply contained: Vec<Contained> should suffice for most use cases. – Sebastian Redl
Please explain your requirements. In other words, what are you trying to achieve? Where are your Contained objects? They have to live somewhere else that outlives the Container. – Acorn
I specifically dont want Cobntained to outlive Container. I wou8ld like objects with the same life time, and I need to reference with pointers &Contained because otherwise I get size not know during complication errors. – teknopaul

1 Answers

0
votes

Answering my own question , it seem Box does what I want

struct Container {
    contained: Box<Option<Contained>>
}

struct Contained {
    id: u64,
}

impl Container {

    pub fn new() -> Container {
        Container {
            contained: Box::new(None),
        }
    }

    pub fn new_contained(&mut self, id: u64) {
        let c= Contained {
            id
        };
        self.contained = Box::new(Some(c));
    }
}

Contained appears to live the same lifetime as Container.