I have the following struct, where Characters is the newtype idiom around Vec<u8>.

#[derive(Encode, Decode, Clone, PartialEq, Eq, RuntimeDebug)]
pub struct OperationData {
  config: BTreeMap<Characters, Vec<Characters>>

Now, If I submit an extrinsic call to save such structure:

  config: { hasher: [ 'Sha2_256', 'Blake3_256' ] },

The structure is stored correctly but upon reading (for instance in polkadot ui) I get:

  config: {
    0x686173686572: [

It appears that the call to Struct.toHuman() does not attempt any conversion of the UTF-8 hex-encoded bytes of the key of the map entry:

h  a  s  h  e  r
68 61 73 68 65 72

It does, however, decode the bytes inside the value of the map entry.

Is there a way to indicate the decoder to decode the map entry keys as well? Any good reason why Map keys are disregarded despite their type association?

1 Answer 1


The toHuman() output is not configurable. Bear in mind that this is a convenience function, not really meant to be used for anything but simple inspection.

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