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Withdraw Asset

Let's use transfer_multiasset to:

  • transfer back asset id = 1 token of parachainId 2007 to parachainId 2000
  • for amount 10000000000000000000000

1. Asset Multilocation​

The assetId Multilocation in the Parachain 2000 is defined by: Multilocation: { parents: 1, interior: X2 [Parachain: 2000, GeneralIndex: 1] }
parachainId 2000 prefixed with 0x00. So the interior bytes are: 0x00 + bytes4(2000) GeneralIndex should be prefixed by 0x05 and u128(1): 0x05 + 1

bytes[] memory interior1 = new bytes[](2);
interior1[0] = bytes.concat(hex"00", bytes4(uint32(2000)));
interior1[1] = bytes.concat(hex"05", abi.encodePacked(uint128(1)));
XCM.Multilocation memory asset = XCM.Multilocation({ 
    parents: 1,
    interior: interior1
});

2. Beneficiary Multilocation​

Let's suppose the beneficiary is the EVM address 0xd43593c715fdd31c61141abd04a99fd6822c8558 of the contract in parachain 2000. The Multilocation is { parents: 1, interior: X2 [Parachain: 2000, AccountId20: { id: *caller address* , network: any }] }.
The interior field is of type H160 (20 bytes EVM address) so prefixed with 0x03 and suffix with 0x00 (network: any). The interior bytes are 0x03 + EVM address + 0x00

bytes[] memory interior = new bytes[](2);
interior[0] = bytes.concat(hex"00", bytes4(uint32(2000)));
interior[1] = bytes.concat(hex"03", msg.sender, hex"00");
XCM.Multilocation memory destination = XCM.Multilocation({
    parents: 1,
    interior: interior
});

3. Weight​

The weight we want to buy in the destination chain, to set the weightlimit to Unlimited, you should use the value 0 for ref_time.

XCM.WeightV2 memory weight = XCM.WeightV2({
    ref_time: 30_000_000_000,
    proof_size: 300_000
});

4. calling XCM precompiles​

Import the XCM precompiles in your contract and call it like this:

address public constant XCM_ADDRESS =
0x0000000000000000000000000000000000005004;

require(
    XCM(XCM_ADDRESS).transfer_multiasset(
        asset,
        amount,
        destination,
        weight
    ),
    "Failed to send xcm"
);

Please check full example in the XCM EVM SDK