pin.rs

#[derive(Debug)]
struct SelfRef {
    text: String,
    ptr: *const String,
}

impl SelfRef {
    fn new(txt: &str) -> Self {
        let text = String::from(txt);
        let mut ret = SelfRef { text, ptr: std::ptr::null() };
        let ptr = &ret.text as *const String;
        ret.ptr = ptr;
        ret
    }
}

fn main() {
    let mut self_ref_a = SelfRef::new("a");
    let mut self_ref_b = SelfRef::new("b");
    println!("[self_ref_a] text: {}, text of ptr: {}", self_ref_a.text, unsafe {
        &*self_ref_a.ptr
    });
    println!("[self_ref_b] text: {}, text of ptr: {}", self_ref_b.text, unsafe {
        &*self_ref_b.ptr
    });

    std::mem::swap(&mut self_ref_a, &mut self_ref_b);
    println!("after swap contents at each position...");

    println!("[self_ref_a] text: {}, text of ptr: {}", self_ref_a.text, unsafe {
        &*self_ref_a.ptr
    });
    println!("[self_ref_b] text: {}, text of ptr: {}", self_ref_b.text, unsafe {
        &*self_ref_b.ptr
    });
}