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I saw the description of the function require_recipient and it says:

Add the specified account to set of accounts to be notified

I would like to understand what's the purpose of receive this notification of a transaction. What are the practical real scenarios examples for dApps that we use it?

I saw that being used on transfer action of eosio.token, I see this notification in my nodeos log but I want to understand it with more details.

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Think of it as sending a carbon copy of the action. Since eosio.token does it with transfer, contracts can monitor and respond to deposits. e.g. if user a transfers EOS to contract b, then b could automatically transfer another token type back to a, creating a simple exchange.

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  • Thanks Todd! Do you mind to give me a smart contract code example in how to "watch" another contract transaction? Like, how can I watch for my contract an eosio.token transfer action?
    – Leo Ribeiro
    May 9, 2018 at 15:19
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    Here's an example. Firefox (fastest) or Chrome (slow load): tbfleming.github.io/cib/…
    – Todd Fleming
    May 9, 2018 at 15:21
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    That's perfect my friend, things are clear now, so if I understood correctly the name of the action in my recipient contract must have the same name of the "emitter" contract and always have two parameters: uint64_t self and uint64_t code, then I execute unpack_action_data with the struct of the "emitter" contract ABI.
    – Leo Ribeiro
    May 9, 2018 at 16:35

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