批准是否需要时间来确认，在 BSC 中如何处理？答案

【问题标题】：Does approve take time to be confirmed, and how to deal with this in BSC?批准是否需要时间来确认，在 BSC 中如何处理？
【发布时间】：2021-07-26 08:42:03
【问题描述】：

您好，我正在使用带有 react 的 web3 做 BSC DApp。我对这个领域很陌生。

我在致电approve 后发现，transfer（或我的情况下是 zapInToken）不会成功，因为抱怨没有足够的津贴。所以我添加了wait allowance 存在 10 秒，但似乎在 10 秒后多次（50% 的机会）津贴仍然不存在。请查看以下代码以获取更多信息。

理论上，approve 将生成一个事务，并且出现的时间取决于。如果是这样，是approve、wait for allowance和transfer的标准模式吗？

谢谢！

const bepContract = getContract(getAddress(from), erc20ABI, library, account)
const tx = await bepContract.approve(getAddress(contracts.zap), weiAmount)
if (!tx) {
    throw new Error('Failed to approve transaction')
}
await waitAllowance(bepContract, account, getAddress(contracts.zap), weiAmount, 10) // <-- and it will stuck here in most time, the code waits for the allowance is present
await getZapContract().zapInToken(getAddress(from), weiAmount, getAddress(to)).then(logInfo).catch(logError)

waitAllowance 如下所示

const waitAllowance = async (
  contract: Contract,
  account: string,
  to: string,
  allowanceNeeded: string,
  timesLeft: number
): Promise<void> => {
  if (timesLeft > 1) {
    const currentAllowance = await contract.allowance(account, to)
    // console.log(`I want ${allowanceNeeded}, and current is ${currentAllowance} `)
    const needed = new BigNumber(allowanceNeeded)
    const current = new BigNumber(currentAllowance.toString())
    if (current.isGreaterThanOrEqualTo(needed)) {
      return
    }
    await new Promise((res) => setTimeout(res, 1000))
    await waitAllowance(contract, account, to, allowanceNeeded, timesLeft - 1)
  }
  throw new Error('wait allowance failed for many times.')
}

【问题讨论】：

标签： ethereum web3js erc20

【解决方案1】：

我想通了，我需要tx.wait，所以工作代码如下：

const bepContract = getContract(getAddress(from), erc20ABI, library, account)
const tx = await bepContract.approve(getAddress(contracts.zap), weiAmount)
if (!tx) {
    throw new Error('Failed to approve transaction')
}
const tx = await waitAllowance(bepContract, account, getAddress(contracts.zap), weiAmount, 10)
const txResult = await tx.wait()
if (txResult.status !== 1) {
    throw new Error('Failed approve')
}
const txZap = await getZapContract().zapInToken(getAddress(from), weiAmount, getAddress(to))
const txZapResult = await txZap.wait()
if (txZapResult.status !== 1) {
    throw new Error('Failed zap')
}

查看doc 了解更多详情

【讨论】：