depositValue not defined in tutorial

[cag]

@zupino noticed this:

In this section of the tutorial, there is an example:

async function buyAllOutcomes() {
    const txResults = await Promise.all([
        [gnosis.etherToken.constructor, await gnosis.etherToken.deposit.sendTransaction({ value: depositValue })],
        [gnosis.etherToken.constructor, await gnosis.etherToken.approve.sendTransaction(event.address, depositValue)],
        [event.constructor, await event.buyAllOutcomes.sendTransaction(depositValue)],
    ].map(([contract, txHash]) => contract.syncTransaction(txHash)))

    // Make sure everything worked
    const expectedEvents = [
        'Deposit',
        'Approval',
        'OutcomeTokenSetIssuance',
    ]
    txResults.forEach((txResult, i) => {
        Gnosis.requireEventFromTXResult(txResult, expectedEvents[i])
    })
}
buyAllOutcomes()

which is missing a definition for depositValue (should be 4 ETH following the tutorial text):

const depositValue = 4e18

[srameshr]

@cag Also what does the following do?

        [gnosis.etherToken.constructor, await gnosis.etherToken.deposit.sendTransaction({ value: depositValue })],
        [gnosis.etherToken.constructor, await gnosis.etherToken.approve.sendTransaction(event.address, depositValue)],
        [event.constructor, await event.buyAllOutcomes.sendTransaction(depositValue)],

What is deposit, approve doing here? Assume intention of the user here is just to buy some tokens and nothing else.

[cag]

@srameshr This is a consequence of the way wrapped ether is specified and the way ERC20 tokens are specified respectively.

In short, deposit comes from the mechanics of W-ETH. Basically, it's so ether can be used as an ERC20 token.

And approve comes from the ERC20 standard itself. Referring to the linked article, you (0x111...) have to authorize the event contract (0x222...) to perform a transferFrom during the execution of buyAllOutcomes.

[cag]

Okay, the original issue should be addressed in the docs at #115 now. I will close this issue when that gets merged, and then I will open another issue wrt srameshr's comment