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Call Contract

Preparing Contract Method Arguments

Suppose you have already deployed a contract that contains a call method as follows:

    fn hello_from(name: String) -> u32 {
            "topic: Hello From".as_bytes(), 
            format!("Hello, Contract. From: {}", name).as_bytes()
        name.len() as u32

To invoke this contract in the blockchain by using pchain_client, you can prepare a JSON file that contains a list of arguments and matches with the call method. For example, this call method takes a string argument. Then, the content of the JSON file should be as follows:

    "arguments": [
        {"argument_type":"String", "argument_value": "\"Alice\""}

This JSON file will be used in the subcommand call as mentioned in the subsequent sections on this page.

Calling Contract

To call a smart contract, submit a transaction with your account nonce and contract address using the pchain_client.

Here is the command to call a contract:

./pchain_client transaction create \
--nonce <NONCE> \
--gas-limit <GAS_LIMIT> \
--max-base-fee-per-gas <MAX_BASE_FEE_PER_GAS> \
--priority-fee-per-gas <PRIORITY_FEE_PER_GAS> \
call \
--method <contract_METHOD> \
./pchain_client.exe transaction create `
--nonce <NONCE> `
--gas-limit <GAS_LIMIT> `
--max-base-fee-per-gas <MAX_BASE_FEE_PER_GAS> `
--priority-fee-per-gas <PRIORITY_FEE_PER_GAS> `
call `
--method <contract_METHOD> `

The gas limit required for the transaction depends on the complexity of the smart contract. For safety reasons, you can always set a higher gas limit. You can also test contract calls on testnet to reassure.

You can follow the instruction in Create Transaction about submiting a transaction through pchain-client.

To query the resulting receipt of the transaction,

./pchain_client query tx --hash <TRANSACTION_HASH> 
./pchain_client.exe query tx --hash <TRANSACTION_HASH>

The commands stored in transaction and command receipts in receipt are following the same order. That means you can always find the corresponding transaction from a command receipt.

Parse Call Result

To parse the response from the contract method, represented in the field named return value , which is in CallResult format, you can use the parse call-result command in ParallelChain Client.

For example, if the contract method returns a u32 integer, the return value is "BAAAAAUAAAA" you can parse the CallResult data structure using the --data-type u32 flag:

pchain_client parse call-result --value BAAAAAUAAAA --data-type u32
./pchain_client.exe parse call-result --value BAAAAAUAAAA --data-type u32

The output will be the parsed value of the CallResult, which in this case is 4. For more details, you can use the help command to see the usage of the tool or take a look at the example argument,json.