Can I save structs in a Mapping?

Question

Is it possible to store structs in a Mapping or any dynamic memory structure in my Solidity SmartContract?

Answer 1

You can store structs as the values of your mapping, not as the key. Here is some more info: http://solidity.readthedocs.org/en/latest/types.html#structs

struct Funder {
  address addr;
  uint amount;
}

struct Campaign {
  address beneficiary;
  uint fundingGoal;
  uint numFunders;
  uint amount;
  mapping (uint => Funder) funders;
}

uint numCampaigns;
mapping (uint => Campaign) campaigns;

Answer 2

Yes, you can.

For example, in the solidity code below. There is a struct User that has a mapping of friends, from address to another struct Friend.

Then there's a mapping of users, from address to User [note that User is a struct].

struct Friend {
    string name;
    string email;
    string phoneNumber;
}

struct User {
    string name;
    string email;
    uint256 balance;
    mapping (address => Friend) friends;
}

mapping (address => User) public users;

So, say a user A has friends B, C, and D. The User can be imagined to look like this:

{
    name: 'A',
    email: [email],
    balance: [balance],
    friends: {
        [address_of_friend_B]: {
            name: 'B',
            email: [email],
            phoneNumber: [phoneNumber],
        },
        [address_of_friend_C]: {
            name: 'C',
            email: [email],
            phoneNumber: [phoneNumber],
        },
        [address_of_friend_D]: {
            name: 'D',
            email: [email],
            phoneNumber: [phoneNumber],
        },
    }
}

And if there are many such User structs, say A, J, Z, ..., the mapping users holds them all:

{
    name: 'A',
    ...
    friends: {...},

    name: 'J',
    ...
    friends: {...},

    name: 'Z',
    ...
    friends: {...},
}

So yes, you can store structs in a mapping.

Answer 3

yes, you can use struct in map like this:

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

contract MyFriends{
    struct Friends{
        string name;
        string[] girlfriends;
        bool isSingle;
    }

    mapping(uint=>Friends) FriendsInfo;
}

wrong codes:

mapping(Friends=>uint) FriendsInfo;