Interacting with the Contract#

Tip

You can also follow these steps in the official desktop wallet for Terra, Terra Station.

Requirements#

Make sure you have set up LocalTerra and that it is up and running:

cd localterra
docker-compose up

You should also have the latest version of terrad by building the latest version of Terra Core. You will configure terrad to use it against your isolated testnet environment.

In a separate terminal, make sure to set up the following mnemonic:

terrad keys add test1 --recover

Using the mnemonic:

satisfy adjust timber high purchase tuition stool faith fine install that you unaware feed domain license impose boss human eager hat rent enjoy dawn

Uploading Code#

Make sure that the optimized build of my_first_contract.wasm that you created in the last section is in your current working directory.

terrad tx wasm store artifacts/my_first_contract.wasm --from test1 --chain-id=localterra --gas=auto --fees=100000uluna --broadcast-mode=block

Or, if you are on an arm64 machine:

terrad tx wasm store artifacts/my_first_contract-aarch64.wasm --from test1 --chain-id=localterra --gas=auto --fees=100000uluna --broadcast-mode=block

This will ask for a confirmation before broadcasting to LocalTerra, type y and press enter.

You should see output similar to the following:

height: 6
txhash: 83BB9C6FDBA1D2291E068D5CF7DDF7E0BE459C6AF547EC82652C52507CED8A9F
codespace: ""
code: 0
data: ""
rawlog: '[{"msg_index":0,"log":"","events":[{"type":"message","attributes":[{"key":"action","value":"store_code"},{"key":"module","value":"wasm"}]},{"type":"store_code","attributes":[{"key":"sender","value":"terra1dcegyrekltswvyy0xy69ydgxn9x8x32zdtapd8"},{"key":"code_id","value":"1"}]}]}]'
logs:
- msgindex: 0
  log: ""
  events:
  - type: message
    attributes:
    - key: action
      value: store_code
    - key: module
      value: wasm
  - type: store_code
    attributes:
    - key: sender
      value: terra1dcegyrekltswvyy0xy69ydgxn9x8x32zdtapd8
    - key: code_id
      value: "1"
info: ""
gaswanted: 681907
gasused: 680262
tx: null
timestamp: ""

As you can see, your contract was successfully instantiated with Code ID #1.

You can check it out:

terrad query wasm code 1
codeid: 1
codehash: KVR4SWuieLxuZaStlvFoUY9YXlcLLMTHYVpkubdjHEI=
creator: terra1dcegyrekltswvyy0xy69ydgxn9x8x32zdtapd8

Creating the Contract#

You have now uploaded the code for your contract, but still don’t have a contract. Create it with the following InitMsg:

{
  "count": 0
}

You can compress the JSON into 1 line with this online tool.

terrad tx wasm instantiate 1 '{"count":0}' --from test1 --chain-id=localterra --fees=10000uluna --gas=auto --broadcast-mode=block

You should get a response like the following:

height: 41
txhash: AEF6F2FA570029A5D4C0DA5ACFA4A2B614D5811E29EEE10FF59F821AFECCD399
codespace: ""
code: 0
data: ""
rawlog: '[{"msg_index":0,"log":"","events":[{"type":"instantiate_contract","attributes":[{"key":"owner","value":"terra1dcegyrekltswvyy0xy69ydgxn9x8x32zdtapd8"},{"key":"code_id","value":"1"},{"key":"contract_address","value":"terra18vd8fpwxzck93qlwghaj6arh4p7c5n896xzem5"}]},{"type":"message","attributes":[{"key":"action","value":"instantiate_contract"},{"key":"module","value":"wasm"}]}]}]'
logs:
- msgindex: 0
  log: ""
  events:
  - type: instantiate_contract
    attributes:
    - key: owner
      value: terra1dcegyrekltswvyy0xy69ydgxn9x8x32zdtapd8
    - key: code_id
      value: "1"
    - key: contract_address
      value: terra18vd8fpwxzck93qlwghaj6arh4p7c5n896xzem5
  - type: message
    attributes:
    - key: action
      value: instantiate_contract
    - key: module
      value: wasm
info: ""
gaswanted: 120751
gasused: 120170
tx: null
timestamp: ""

From the output, you can see that your contract was created above at: terra18vd8fpwxzck93qlwghaj6arh4p7c5n896xzem5. Take note of this contract address, as you will need it for the next section.

Check out your contract information:

terrad query wasm contract terra18vd8fpwxzck93qlwghaj6arh4p7c5n896xzem5
address: terra18vd8fpwxzck93qlwghaj6arh4p7c5n896xzem5
owner: terra1dcegyrekltswvyy0xy69ydgxn9x8x32zdtapd8
codeid: 1
initmsg: eyJjb3VudCI6MH0=
migratable: false

You can use the following to decode the Base64 InitMsg:

echo eyJjb3VudCI6MH0= | base64 --decode

This will produce the message you used when initializing the contract:

{ "count": 0 }

Executing the Contract#

Let’s do the following:

Reset count to 5
Increment twice

If done properly, you should get a count of 7.

Reset#

First, to burn:

{
  "reset": {
    "count": 5
  }
}

terrad tx wasm execute terra18vd8fpwxzck93qlwghaj6arh4p7c5n896xzem5 '{"reset":{"count":5}}' --from test1 --chain-id=localterra --fees=1000000uluna --gas=auto --broadcast-mode=block

Incrementing#

{
  "increment": {}
}

terrad tx wasm execute terra18vd8fpwxzck93qlwghaj6arh4p7c5n896xzem5 '{"increment":{}}' --from test1 --chain-id=localterra --gas=auto --fees=1000000uluna --broadcast-mode=block

Querying count#

Check the result of your executions!

{
  "get_count": {}
}

terrad query wasm contract-store terra18vd8fpwxzck93qlwghaj6arh4p7c5n896xzem5 '{"get_count":{}}'

Expected output:

query_result:
  count: 7

Excellent! Congratulations, you’ve created your first smart contract, and now know how to get developing with the Terra dApp Platform.

What’s Next?#

We’ve only walked through a simple example of a smart contract, that modifies a simple balance within its internal state. Although this is enough to make a simple dApp, you can power more interesting applications by emitting messages, which will enable you to interact with other contracts as well as the rest of the blockchain’s module.

Check out a couple more examples of smart contracts using Terra’s smart contract repo.

Interacting with the Contract

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