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MakerDao's Dai and Delphus

Groundbreaking, Seamless Dai Integration in Existing DApps

Price volatility is the Achilles’ heel of a distributed application, or DApp for short. Nobody wants to deposit funds when Ether dipped 30% in the last month. And, while stablecoins like Dai can solve this issue, they have notoriously poor documentation, as we mentioned in our previous post. Furthermore, most existing DApps are already designed around Ether, which is relatively easy to process, and converting them to use DAI is an arduous and under-documented task.

The UX Problem

Using Dai also poses another issue: the user experience. If a smart contract only accepts Dai, new users will have to manually go to an exchange (of which there are few) to convert their Ether to Dai, then return to the DApp and deposit their Dai. Then, when taking out Dai, they have to manually convert it back to Ether to sell it for fiat on an exchange.

Enter Oasis.Direct.

Oasis.Direct is the prime example of what the UX for a decentralized app could be  a one-click transaction converts your Ether to Dai, without any manual ordering or price setting. Moreover, by integrating it into Dai-accepting smart contracts, it has the potential to make them far easier to use.

Step 1: Connecting to Maker Contracts

First, let’s take a (slightly simplified) look at how the entrypoint for our StudyManager contract looked like before Dai integration:

Ignore the other parameters, what matters is that it’s a payable function to which the user can send Ether. That Ether is then held by the contract and recorded in the new study’s paymentPool.

To convert this function to accept Dai, we have to retool it a little:

We’ve changed the contract to look much like a function that accepts ERC20 tokens which it should, since Dai is, at its heart, an ERC20 token.

However, there are two issues with this approach:

  1. The user still has to manually convert their Ether to Dai.
  2. The user has to manually call dai.approve(YOUR_CONTRACT_ADDRESS, tokenAmount) before calling this function, thanks to the design of the ERC20 standard. This means that the user has to approve two transactions.

Thankfully, we can solve both of these issues simultaneously:

Step 2: Interfacing with OasisDEX

OasisDEX is a decentralized exchange that converts ETH to DAI, running on both the Kovan test network and the main network. Its contract addresses (under “market”), along with Dai’s Kovan and mainnet addresses, can be found in the source code repository.

By interacting with OasisDEX, we can simplify the user flow, automatically converting deposited Ether to Dai for long-term storage.

Let’s see an example from our code:

(Contract interfaces from Oasis.Direct’s code.)

Here, the contract does four things:

  1. It deposits the paid Ether into the WETH contract, which is needed to trade on OasisDEX. Our contract now owns msg.value in WETH.
  2. It gives OasisDEX approval to use as much WETH as it needs to trade it to Dai.
  3. It executes an automatic trade from WETH → DAI, requiring an outcome of at least minBuyAmt DAI or else the trade will fail.
  4. It creates the study as we did in the previous step.

Note that the function has to be passed in the “minimum buy amount” of Dai that they want; it specifies the minimum exchange rate, in effect. You can calculate this on the DApp end by calling (with ethers.js/web3):

Which you can do invisibly before sending the createStudy transaction, in this case.

Step 3: Mocking Maker

Now, there’s one downside with this approach: to test your contracts in the future, you’ll have to use the live OasisDEX contracts on Kovan or the main network. This obviously doesn’t play very well with automated testing like Truffle, as each test would require actual Kovan/mainnet Ether.

First, we tried a new way of testing: with the tool ganache-cli, you can actually do a virtual chain fork by connecting to a mainnet/Kovan node and effectively creating a development blockchain that starts with all the state of the live network. This would let you test cheaply, without incurring costs on the live network, but while still connecting to “real” MakerDAO contracts.

Unfortunately, we ran into issues where our contracts either failed to deploy or didn’t work properly with this setup, so ultimately we ditched it for a more traditional, if more annoying, approach.

Let’s deploy all the Maker contracts on the Truffle development network!

The full code is pretty long, but I’ve put it on a GitHub gist at the end of the post if you’d like to use it. Here are the major steps:

  1. Deploys OasisDEX, WETH, and a FakeDAI contract (just a mintable ERC20 token) from /contracts/maker/.

  2. Whitelists the WETH and FakeDAI pair for fake-trading. This is necessary to prevent the OasisDEX contract from erroring on “untrusted” token pairs.

  3. Creates the WETH to DAI trading side of the exchange and the DAI to WETH side.

    To do this, you have to deposit WETH, approve it for use by OasisDEX, and make a fake WETH → DAI offer at a fake exchange rate. For the other side, you have to mint some fake DAI, approve it for use by OasisDEX, and make a fake DAI → WETH offer.

This creates a marginally-functional OasisDEX contract on the development network which you can use to mock Dai trading.

And there you go! That’s how you convert a contract accepting Ether to one that seamlessly converts it to Dai for long-term storage.


This code was used in our product Delphus, a DApp revolutionizing the management of clinical data in scientific studies. Find out more there!

Appendix

Other interesting links:

Development Truffle migration script:

Categories
MakerDao's Dai and Delphus

Rationale for Tutorial

While Dai is a useful tool and allows for stability of a platform, there are not many instructions on how to implement this token into either a new Distributed Application or an existing one. Further, existing documentation does not appear to exist with few understandable comments, which, to be fair, is somewhat understandable with such a new implementation.

MakerDao’s official chat has been more than helpful, but we believe that it may allow for easier integration if there was a documented journey from start to finish, including the most common errors found, it may be useful for others.

We will be showing snippets of our code as we implement them, and our full source code will be released at the public release (we aim to be open source).

Thank you for joining us on this journey, and we hope that it ends up working for both you and us.

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MakerDao's Dai and Delphus

Why does Delphus use Dai?

If you don’t know what Delphus is and would like to know more, please check out our earlier post here as well as our website here.

As you may already know, the one issue most have with cryptocurrencies is the overall volatility of most networks.

For example, Bitcoin, mostly due to surrounding hype and a positive relationship between investors and miners, spiked in prices, reaching $20,000 back in December, but then “normalizing” down to its current price of around $8,000.

These increasingly different prices, often with no correlation to any conventional market trends to the average user, provide for a marketplace not useful for many cases in which a static amount of value may need to be stored. This is the case with Delphus as the researcher -> participant payments cannot change in value throughout the duration of the study.

There are many viable options for addressing this issue, with new stablecoins appearing every so often. The stablecoin most prominent, trusted and well supported by developers as of now is MakerDao’s Dai. It is tied 1:1 with the US dollar with very few deviations of non-discernible value (>.01 cents). It is collateralize using valuable assets in the open-source Maker contract.

For this reason, it is far easier for researchers to set static payments that can be distributed through smart contracts, rather than relying on the rise and fall of a cryptocurrency. Since we rely on the Ethereum Blockchain, we can use the ERC20 token, Dai, in order to keep stable prices and allow both researchers and patients an easy way to receive non-volatile payments.

This allows us to garner better communication between the researcher and the patient, while reducing the risk of patients not receiving their specified payment or complaining about how what could be $1,000 the first day, is $5 the next day (they probably won’t be complaining if the price increases). Further, as Dai is being continuously developed and scaled with them introducing more collaterals to their system, it is ideal for the ever-expanding field of medicine and clinical trials.

Thus, we arrived at the logical conclusion of incorporating Dai into our project and we’d like to share with any interested parties, the entire process of its integration.


edited product name from reblock to Delphus