Working with Different Action Return Types

Prerequisites

• Before proceeding forward, ensure that you have completed Getting Started section and that you have followed Getting Started Documentation Diagram.
• This page assumes you are familiar with Smart Contract Basics.

REMINDER

The install process has already set up the wallet for the root user. To interact with clio, ensure you are on the root user. Run sudo su - to switch to the root user.

Steps

1. Create a new directory for our contract

mkdir -p returndemo && cd returndemo

2. Create the contract file returndemo.cpp

#include <sysio/sysio.hpp>
#include <string>
#include <vector>

class [[sysio::contract]] returndemo : public sysio::contract {
public:
    using contract::contract;

    struct [[sysio::table]] tmp {
        uint32_t id = 1;
        std::vector<uint16_t> list{ 1, 2 };
    };

    [[sysio::action]]
    std::string rstring(const std::string & str) { 
        return str;   
    }

    [[sysio::action]]
    uint16_t ruint(uint16_t i) { 
        return i;     
    }

    [[sysio::action]]
    tmp rtmp() { 
        return tmp{}; 
    }
};

3. Build the Contract

cdt-cpp -abigen  -contract returndemo -o returndemo/returndemo.wasm returndemo.cpp -I include

4. Deploy the Contract

Before deploying, ensure you have an open wallet and account to deploy the contract to.

note

In Wire ecosystem, deploying a smart contract requires an account; an account can own one smart contract instance and a smart contract instance must be deployed to an account. Each account functions as a distinct namespace for the contract, which means that the contract’s code and its state are encapsulated within that account.

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4.1 Retrieve public key

Before proceeding, make sure you have the public key available from the key pair that was created when setting up your wallet (key pair is also listed here). If you haven't yet created a wallet or a key pair, you can do so by following the instructions here.

export PUBLIC_KEY=<public-key-value>

4.2. Create the account that we will deploy the contract to

clio create account sysio returndemo $PUBLIC_KEY -p sysio@active

4.3. Issue a contract policy to returndemo account

nodeownera's credentials(those should be already imported in your wallet from wire-cli installation):

clio wallet keys_by_name --password "$(cat /opt/wire-network/secrets/wallet_password.txt)" | jq '.[] | select(.[0] == "nodeownera")'

Issue the policy:

clio push action sysio.roa addpolicy '{"owner": returndemo, "issuer": nodeownera, "net_weight": "0.0100 SYS", "cpu_weight": "0.0100 SYS", "ram_weight": "0.0010 SYS", "time_block": 1, "network_gen": 0 }' -p nodeownera@active

4.4 Deploy the compiled contract

                 [account]     [WASM dir]  [permission level] 
clio set contract returndemo  returndemo -p  returndemo@active

Now that our contract is deployed, we can interact with it using the clio push action command. Here are some examples:

> clio push action returndemo rstring '{"str":null}'  -p returndemo@active

executed transaction: bd82b06bf56a3fb61564cb566b2412ec60ade76b4aa683980150428d94d480dd  96 bytes  314 us
#    returndemo <= returndemo::rstring          {"str":""}
=>                                return value: ""

> clio push action returndemo rstring '{"str":"test"}'  -p returndemo@active

executed transaction: 69366ff9edad9a16a1d5f9181ad3415512f7bfaca4bd15ce2be38163a6642be1  104 bytes  148 us
#    returndemo <= returndemo::rstring          {"str":"test"}
=>                                return value: "test"

> clio push action returndemo ruint '{"i":42}'  -p returndemo@active

executed transaction: f90221965a81c53da7d8f5b49a2be34994ed6ed463afe80f4f23f48f7ece5fb9  96 bytes  195 us
#    returndemo <= returndemo::ruint            {"i":42}
=>                                return value: 42

The rtmp action output, returning a default tmp object, looks like this:

> clio push action returndemo rtmp '{}'  -p returndemo@active

executed transaction: 42386687d94695d77d67cf901cf8d1a4f83ac9f89382f0b01f3fb51267cc21cd  96 bytes  110 us
#         returndemo <= returndemo::rtmp        ""
=>                                return value: {"id":1,"list":[1,2]}

If the length of the return value string is more than 100 chars, the string will be truncated to the first 100 chars and three dots ... will be added at the end. It's similar to what clio does to action parameters output.

> clio push action returndemo rstring '{"str":"qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq"}'  -p returndemo@active
executed transaction: 985b4f7acefafd018659a544b3a5c3288d8ac76e53a5747e928a85d49256d4a2  248 bytes  243 us
#    returndemo <= returndemo::rstring          {"str":"qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq...
=>                                return value: "qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq...

When the ABI doesn't include the return type definition for an action, the return value will be displayed in hexadecimal format, like this:

=>                          return value (hex): 1400000001000770656e64696e6700000000