Error: User defined types not provided

[naveed949]

while testing program, getting following error.
CMD: anchor test
ErrorLog:

0 passing (10s)
1 failing

1. blindbox
   Is initialized!:
   Error: User defined types not provided
   at Function.fieldLayout (node_modules/@project-serum/anchor/dist/cjs/coder/idl.js:96:31)
   at typeDef.type.fields.map (node_modules/@project-serum/anchor/dist/cjs/coder/idl.js:126:36)
   at Array.map ()
   at Function.typeDefLayout (node_modules/@project-serum/anchor/dist/cjs/coder/idl.js:125:54)
   at AccountsCoder.idl.accounts.map (node_modules/@project-serum/anchor/dist/cjs/coder/accounts.js:20:46)
   at Array.map ()
   at new AccountsCoder (node_modules/@project-serum/anchor/dist/cjs/coder/accounts.js:19:38)
   at new Coder (node_modules/@project-serum/anchor/dist/cjs/coder/index.js:32:25)
   at new Program (node_modules/@project-serum/anchor/dist/cjs/program/index.js:54:23)
   at fs.readdirSync.forEach (node_modules/@project-serum/anchor/dist/cjs/workspace.js:71:44)
   at Array.forEach ()
   at Object.get (node_modules/@project-serum/anchor/dist/cjs/workspace.js:64:39)
   at Context.it (tests/blindbox.js:16:38)
   at processImmediate (internal/timers.js:443:21)

   After debugging I've found following struct is causing issue.
   IDL json formatt:
   { "name": "Boxes", "type": { "kind": "struct", "fields": [ { "name": "authority", "type": "publicKey" }, { "name": "boxes", "type": { "defined": "HashMap<u32,NftBox>" } } ] } }

Program version of same struct:
`

#[account]
pub struct Boxes {

pub authority: Pubkey,
pub boxes: HashMap<u32, NftBox>,
} `

Note: I've also tried BTreeMap instead of HashMap but getting same issue.
Please help me

[armaniferrante]

HashMaps aren't currently supported in the IDL.

[naveed949]

okay @armaniferrante can you please tell what collections are implemented from std::collections as I need to store key-value data in my program ?
or please suggest me any for this purpose.

[armaniferrante]

You can approximate a map by using program-derived addresses PDAs. Seeds are your keys, values are your accounts.

[naveed949]

Trying to understand @armaniferrante
For example:
I want to store n number of Boxes in my account where each Box is a kind of NFT and identified by its ID.
so how will an PDA will store these all n number of Boxes.
OR
are you saying I'll need n number of PDAs to store 1 Box per PDA.
As for now what I can understand one PDA/account can store only one Box, due to the unavailability of map.

please correct me if missing anything