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Pact Local API queries

Chainweb supports the use of the Pact smart contract language, including the local API endpoints defined in the documentation. Using the local API endpoints on any Chainweb node, you can dry-run Pact smart contracts using actual data in the coin contract tables. This is perfect for checking the viability of your smart contracts, as well as to check account data without necessarily having to spend tokens!


Follow the instructions at the Welcome to Pact section to get started with Pact learning the basics. For a more straightforward and technical introduction, just readthedocs.

In particular, for any script going on Chainweb, you'll need to understand the API request format.

Creating A Local API Request

A local query does not need to make use of any metadata, env data, or signers, so a minimalist API request format is relatively simple:

(code|codeFile): <code goes here>
keyPairs: []

For example, if one wanted to check their balance, the following request format would be sufficient:

code: (coin.get-balance "<account name>")
keyPairs: []

Once one has such a yaml, issue pact -l -a <my-script-name>.yaml. The following output should look something like this:

{"hash":"<some hash>","sigs":[],"cmd":"{\"networkId\":null,\"payload\":{\"exec\":{\"data\":null,\"code\":\"(coin.get-balance \\\"<account-name>\\\")\"}},\"signers\":[],\"meta\":{\"creationTime\":0,\"ttl\":0,\"gasLimit\":0,\"chainId\":\"\",\"gasPrice\":0,\"sender\":\"\"},\"nonce\":\"2019-11-03 01:58:38.266437 UTC\"}"}

You can see that most entries are null, and the metadata has been stubbed out for you. If you wish to enter explicit entries for any of these fields, you are welcome, but they will not be used. It is, however, a great way to practice.

Sending the Command to Chainweb

Once one has a command at the ready, they may send it as JSON using their favorite program to the local pact endpoint of any Chainweb node on a chain where the account exists. Using the us-e2 bootstrap node as an example, sending to the local endpoint looks something like the following:

curl -X POST \ \
-H 'Content-Type: application/json' \
-d '{"hash":"SLxYfnaUCH4XjzdK7e4i0Keo3UMjX8axXFp54jT9xS4","sigs":[{"sig":"b1ce5740c230779ae28d28e6f838fe79dfde00f8443f77a1082d302fe55906d56165ce096234ce870dff03e62ee741460230892b0aadf6ae5e29ae0d2984b80f"}],"cmd":"{\"networkId\":\"mainnet01\",\"payload\":{\"exec\":{\"data\":null,\"code\":\"(coin.details \\\"ff5f5b2ca782a7586292507bddebdf89a3df1e7438071ee98fd3c09abdb53ea4\\\")\"}},\"signers\":[{\"pubKey\":\"0f5fbfa90eadd843f18c6ecefc7691926073767f5abf33ef9dbf997fe544c775\"}],\"meta\":{\"creationTime\":0,\"ttl\":100000,\"gasLimit\":1000,\"chainId\":\"3\",\"gasPrice\":1.0e-2,\"sender\":\"emily\"},\"nonce\":\"2019-11-02 01:15:52.46679 UTC\"}"}'

If this call is successful, then a result is returned immediately with the requested data:

"balance": <some decimal number here>,

And voilá! You have your balance.

Automating Pact Local calls

The community has provided some wonderful scripts to automate this process, and more are always welcome. Especially if they are robust. Here are a few:

More are welcome. Make sure to ping us when you come up with something so we can add it to the Pact script hall of fame!