TypeError: Cannot read property 'call' of undefined

Question

I am trying to read a mapping inside my smart contract that looks like this:

mapping(address => User) public users;

My web3js code looks like this. I am trying to read mapping users inside the smart contract:

var contractAddress='0x3aacc70dced50f8c6c1951f27d505d2ad165b373';
var contractInstance = new web3.eth.Contract(abi,contractAddress);
contractInstance.users.call(web3.eth.accounts[0], function(err, result){
 if(!err){
    alert(result)
 }
 });

However I get the error like below:

TypeError: Cannot read property 'call' of undefined

Can someone help me resolve this

Answer 1

You can't call a mapping public getter without sending a key with it. Also you are returning a Struct which is not possible yet (AFAIK) check this answer for more : https://github.com/trufflesuite/truffle/issues/302

If that is not fix your problem, you may need to check your .json built by truffle or try to deploy again.

Answer 2

When arrays are returned with public getters, you need to specific the index that you are looking for.

You may find the following article useful structs from public functions and/or just manually loop through each index and add it to a json object.