Trait frame_support::dispatch::EncodeLike[][src]

pub trait EncodeLike<T = Self>: Encode where
    T: Encode
{ }
Expand description

A marker trait that tells the compiler that a type encode to the same representation as another type.

E.g. Vec<u8> has the same encoded representation as &[u8].

Example

fn encode_like<T: Encode, R: EncodeLike<T>>(data: &R) {
    data.encode(); // Valid `T` encoded value.
}

fn main() {
    // Just pass the a reference to the normal tuple.
    encode_like::<(u32, u32), _>(&(1u32, 2u32));
    // Pass a tuple of references
    encode_like::<(u32, u32), _>(&(&1u32, &2u32));
    // Pass a tuple of a reference and a value.
    encode_like::<(u32, u32), _>(&(&1u32, 2u32));
}

Warning

The relation is not symetric, T implements EncodeLike<U> does not mean U has same representation as T. For instance we could imaging a non zero integer to be encoded to the same representation as the said integer but not the other way around.

Limitation

Not all possible implementations of EncodeLike are implemented (for instance Box<Box<u32>> does not implement EncodeLike<u32>). To bypass this issue either open a PR to add the new combination or use Ref reference wrapper or define your own wrapper and implement EncodeLike on it as such:

fn encode_like<T: Encode, R: EncodeLike<T>>(data: &R) {
    data.encode(); // Valid `T` encoded value.
}

struct MyWrapper<'a>(&'a (Box<Box<u32>>, u32));
impl<'a> core::ops::Deref for MyWrapper<'a> { // Or use derive_deref crate
    type Target = (Box<Box<u32>>, u32);
    fn deref(&self) -> &Self::Target { &self.0 }
}

impl<'a> parity_scale_codec::WrapperTypeEncode for MyWrapper<'a> {}
impl<'a> parity_scale_codec::EncodeLike<(u32, u32)> for MyWrapper<'a> {}

fn main() {
    let v = (Box::new(Box::new(0)), 0);
    encode_like::<(u32, u32), _>(&MyWrapper(&v));
}

Implementations on Foreign Types

impl EncodeLike<Entry> for Entry

Implementors