Unable to understand how priceFeed.version() works

[jasjyotsinghjaswal]

1. At 2:47:00 We implemented the interface and alternatively copied the interface code AggregatorV3Interface, regardless there was no implementation for version method in the interface, so how are we still able to make the function calls .

2. Also can you explain the difference between interface and abstract contract in Solidity

[PatrickAlphaC]

1. There is a function for version actually! https://github.com/smartcontractkit/chainlink/blob/8c1e22e02fd218d155a6868ee74a0e602ec58003/contracts/src/v0.6/interfaces/AggregatorV3Interface.sol#L20

Just keep in mind, an interface doesn't need to define what a function does, it just needs to define what the function looks like, aka the function name, input parameters and return types.

2. Abstract contracts are contracts with at least 1 function undefined, interfaces have all the functions undefined.