Which's the type of agent variable? How can I remove the type var (to remove the warning in my code). Please ignore the comments.

    uint nonce;
    struct Agent {
        uint idAgent;
        uint[] O_preferences;
    mapping(address => Agent) public agents;
    address[] public agentsInfo;
    /// @notice Crea un nuevo agente con sus parámetros
    /// @param _address dirección del agente 
    /// @param _idAgent id del agente
    /// @param _O_Preferences preferencias del agente
    function setAgent(address _address, uint _idAgent, uint[] _O_Preferences) public {
        var agent = agents[_address];
        agent.idAgent = _idAgent;
        agent.O_preferences = _O_Preferences;
        agentsInfo.push(_address) -1;

Last question: what does that -1 mean (on the last line)?

Thanks in advance!

1 Answer 1


The variable agent is a reference to an item from agents:

var agent = agents[_address];

Now agents is a mapping from address to Agent.

So you can replace var with Agent (with storage access)

Agent storage agent = agents[_address];

The -1 at the end of agentsInfo.push(_address) - 1 does nothing.

In old solidity version .push(..) returned the new array's length, so .push(..) - 1 is the position where the new item was stored.

In this particular case since the result is not assigned to anything it serves no purpose. If you remove - 1 it semanticly works the same.

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