Approve & Deposit

Aave LendingPool contract is the main contract of the protocol. It exposes all the user-oriented actions that can be invoked using either Solidity or web3 libraries.

https://docs.aave.com/developers/v/2.0/the-core-protocol/lendingpool

• LendingPool contracts are upgradable. This means that their addresses may change in the future.

• To prevent third party DApps from falling behind, Aave provides a LendingPoolAddressesProvider contract that will never be upgraded.

• This is used to retrieve the latest LendingPool. As soon as we have the latest LendingPool, we can start depositing.

To interact with ILendingPoolAddressesProvider contract, we will need its address and ABI.

ILendingPoolAddressesProvider

ABI

To obtain the ABI, we will use an interface.

Since we only require a select few functions: deposit, withdraw and so forth, we can create our own interface.

• create ILendingPoolAddressesProvider.sol in interfaces folder.

• either create your own interface by defining the functions (refer to etherscan or github)

• 

• or, just copy aave's interfaces

Address

Addresses Provider -> Deployed Contracts Section

https://docs.aave.com/developers/v/2.0/deployed-contracts/deployed-contracts

Add these to brownie-config.yaml

def get_lendingpool():
    # create lending_pool_addressess_provider contract object
    lending_pool_addressess_provider = interface.ILendingPoolAddressesProvider(config["networks"][network.show_active()]["lending_pool_addressess_provider"])
    lending_pool = lending_pool_addressess_provider.getLendingPool()
    return lending_pool

Lending Pool

ABI -> interface

• https://docs.aave.com/developers/v/2.0/the-core-protocol/lendingpool/ilendingpool

• Change import path from local directories to github

ILendingPool.sol

Original:

import {ILendingPoolAddressesProvider} from './ILendingPoolAddressesProvider.sol';
import {DataTypes} from './DataTypes.sol';

Modified:

import {ILendingPoolAddressesProvider} from '@aave/contract/interfaces/ILendingPoolAddressesProvider.sol';
import {DataTypes} from '@aave/contract/protocol/libraries/types/DataTypes.sol';

compile after, to check if interfaces are correct.

brownie-config.yaml

Address

We will get the address by calling getLendingPool() from the ILendingPoolAddressesProvider

def get_lendingpool():
    # create lending_pool_addressess_provider contract object
    lending_pool_addressess_provider = interface.ILendingPoolAddressesProvider(config["networks"][network.show_active()]["lending_pool_addressess_provider"])
    #get lending pool address
    lending_pool = lending_pool_addressess_provider.getLendingPool()
    return lending_pool

Code thus far

aave_borrow.py

from code import interact
from distutils.command.config import config
from scripts.helpful_scripts import get_account
from brownie import network, config, interface
from scripts.get_weth import get_weth

def main():
    account = get_account()
    deposit_token = config["networks"][network.show_active()]["weth_token"]
    # if no WETH, get_weth()
    # local mainnet fork can use dummy acocunts to get WETH
    # since local mainnet fork, can use dummy accounts. if actual mainnet/testnet then use private key account.
    if network.show_active() in ["mainnet-fork"]:
        get_weth()

    # Get lending pool contract
    lending_pool_address = get_lendingpool()
    lending_pool = interface.ILendingPool(lending_pool_address)
    print(f"....Lending pool contract: {lending_pool_address}....")

    # Approve sending our ERC20(WETH) tokens
    approve_erc20(deposit_amount, lending_pool.address, deposit_token, account)

      
def get_lendingpool():
    # create lending_pool_addressess_provider contract object
    lending_pool_addressess_provider = interface.ILendingPoolAddressesProvider(config["networks"][network.show_active()]["lending_pool_addressess_provider"])
    #get lending pool address
    lending_pool = lending_pool_addressess_provider.getLendingPool()
    return lending_pool

helpful_scripts.py

brownie-config.yaml

Approve

Before we can deposit we must approve Aave's contract to use our WETH tokens. This is done with the approve function.

ERC20.sol

Because DApps (decentralized applications) use smart contracts to execute transactions, you must give permission for the smart contract to transfer up to a certain amount of your token (allowance).

To reiterate, transacting with ERC-20 tokens is a 2-step process:

1. Approval of token allowance

2. Submission of transaction

approve_erc20()

approve_erc20

def approve_erc20(amount,spender, erc20_address, account):
    print("....Approving ERC20 token...")
    # get ERC20 interface: https://github.com/PatrickAlphaC/aave_brownie_py_freecode/tree/main/interfaces
    erc20 = interface.IERC20(erc20_address)

    # approve(address spender, uint256 value)
    tx = erc20.approve(spender,amount,{"from": account})
    tx.wait(1)
    print("....Approved....")
    return tx

In a generic implementation, we would create IERC20.sol in our interfaces folder, and pass the ERC20 token contract into the interface as above. Subsequently, we call on the token contract to approve setting our allowance for another 3rd party contract (via erc20.approve).

aave_borrow.py

Added to main():

• approve_erc20(deposit_amount, lending_pool.address, deposit_token, account)

• deposit_amount as global variable

since we are always runnning on mainnet-fork, set default = mainnet-fork in brownie-config.yaml, under the networks section.

Deposit

When depositing, the LendingPool contract must haveallowance()to spend funds on behalf ofmsg.sender for at-leastamount for the asset being deposited. This can be done via the standard ERC20 approve() method.

The referral program is currently inactive and you can pass0 as thereferralCode.

In future for referral code to be active again, a governance proposal, with the list of unique referral codes for various integration must be passed via governance.

We will the below to main():

addition

## Deposit: deposit(address asset, uint256 amount, address onBehalfOf, uint16 referralCode)
# referralCode is deprecated - pass a 0 as parameter
print("....Depositing....")
tx = lending_pool.deposit(deposit_token_address, deposit_amount, account.address,0, {"from": account})
tx.wait(1) # wait one block
print("....Deposited!....")

aave_borrow.py