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I want to get a random value in my smart contract to provide a fair distribution of different tokens.

I read that using Harbinger to get values and use it for entropy could be the good way to do. But I can't figure out how to make a call to the deployed normalizer contract using Smartpy and then retrieve the given price value.

This is actually the method that I implemented but I get an error when I run it on the Granada network and I don't know how to retrieve the price value (I don't know where and how to pass a callback name)

@ sp.entry_point
def call_oracle(self):
    params_type = sp.TPair(sp.TString, sp.TAddress)
    oracle_params = sp.contract(params_type, self.data.oracle_address, entry_point="get").open_some()
    data_to_be_sent = sp.pair(sp.string("XTZ-USD"), sp.self_address)
    sp.transfer(data_to_be_sent, sp.mutez(0), oracle_params)
  • So my first question is, can I use directly the deployed Harbinger normalizer smart contract or do I need to develop and deploy my own ?
  • And second question, does anyone have an implementation example to call the normalizer smart contract from another smart contract using Smartpy ?

Thanks for your attention.

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This project tezos-randomizer uses the Harbinger Oracle.

Try to have a look at this file: https://github.com/asbjornenge/tezos-randomizer/blob/c4e2134daa724c6338c01daba055b85397ffd97e/randomizer.py#L169

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  • Thank you for your answer. But as I see the Caller contract call the Randomizer contract which has an entropy value. Does it mean that this entropy should be set by the contract administrator "by hands" ? Because I don't see any call to an oracle there.
    – Noctambul
    Commented Dec 1, 2021 at 14:03
  • I've never used the harbinger oracle. But I think you want to do this: github.com/asbjornenge/tezos-randomizer/blob/…
    – Rodrigo Quelhas
    Commented Dec 1, 2021 at 14:35
  • Thanks, I missed this one ! I'll try that :) !
    – Noctambul
    Commented Dec 1, 2021 at 15:44

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