Solidity Encoding – How to Encode a Struct with Solidity

abiencoderv2bytessoliditystruct

Is it possible to encode a struct in Solidity without serializing each variable separately?

Something like:

struct MyStruct {
   uint x;
   uint y;
}

MyStruct storage myStruct = MyStruct({
   x: 11,
   y: 12
});

bytes memory data = abi.encode(myStruct, (MyStruct));

Or in assembly?

Best Answer

If you just want to store this on your contract, solidity structs are already stored encoded in storage.

Just define a data member as struct and assign values, it will be properly encoded.

In case you want to send this as a function parameter, you can just pass the struct (if that's the input type) and it will also be encoded properly.

Related Solutions

Solidity – Initializing Structs to Storage Variables

The former doesn't work because a SomeStruct storage is a pointer to the contract's storage space, and the way Solidity handles storage requires deriving that address from the organization of the structs you're writing it to - that is, its address in storage is directly dependent on the variable you're going to store it in. Without knowing what variable it's going in, it can't write to storage.

Your second snippet works because it first copies the data into a known location in storage, then copies it a second time to a new location, but as you'd expect, that's very inefficient. A better approach is to make your temporary struct in memory:

contract StructExample {

    struct SomeStruct {
        int someNumber;
        string someString;
    }

    SomeStruct[] someStructs;

    function addSomeStruct() {
        SomeStruct memory someStruct = SomeStruct(123, "test");
        someStructs.push(someStruct);
    }
}

Solidity will automatically generate code that copies the struct data from memory into storage.

Web3.py – How to Transact Call with Struct Parameter

For anyone looking for this, the proper way to do it is with encode_abi from python package eth_abi

Best Answer

Related Solutions

Solidity – Initializing Structs to Storage Variables

Web3.py – How to Transact Call with Struct Parameter

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