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  • About Bancor Network
    • Bancor V3
    • Bancor Basics
      • About Bancor
      • What Can I Do With Bancor?
      • Liquidity Pools
      • Single-Side Liquidity
      • Why Use Bancor?
      • Resources
    • Resources for DAOs
      • Token Whitelisting Requirements
      • Liquidity Mining
        • Auto Compounding Rewards
          • How Auto Compounding Rewards work
          • How to Create an Auto Compounding Rewards Program
          • Custom Rewards Programs
        • Dual Liquidity Mining
        • Standard (External) Rewards
    • Security & Audits
      • Multisig Rights
      • Oracles
      • DAO MSIG Intervention Policy
  • Contracts & Functions
    • Contracts
    • Write Functions
      • Transaction Prerequisites
        • approve() / allowance()
      • Trading
        • tradeBySourceAmount()
        • tradeByTargetAmount()
        • Trading Troubleshooting
      • Adding Liquidity
        • deposit()
        • depositFor()
        • Deposit Troubleshooting
        • depositAndJoin()
      • Removing Liquidity
        • Initiating Cooldown
          • initWithdrawal()
        • withdraw()
        • cancelWithdrawal()
        • Withdraw Troubleshooting
      • Flashloan
        • flashLoan()
        • Flashloan Troubleshooting
      • Migrating Liquidity to v3
        • Migrating Bancor positions to v3
          • migratePositions()
          • migratePoolTokens()
          • Errors and Troubleshooting
        • Migrating from Uniswap v2
          • migrateUniswapV2Position()
        • Migrating from Sushiswap
          • migrateSushiSwapV1Position()
      • Rewards
        • join()
        • stakeRewards()
        • autoProcessRewards()
        • claimRewards()
        • leave()
      • Surplus migration
        • withdrawPOL()
      • Network Fees
        • burnNetworkFees()
    • Read Functions
      • Rewards
        • Standard rewards
          • Identify if a program exists
            • Auto Compounding
            • Standard Rewards
          • programIds()
          • programs()
          • providerProgramIds()
          • pendingRewards()
          • latestProgramId()
          • isProgramActive()
          • isProgramEnabled()
          • providerStake()
          • programStake()
          • providerRewards()
        • Auto compounding rewards
          • bnToken balance
          • isProgramActive()
          • isProgramPaused()
          • pools()
          • program()
          • programs()
      • Liquidity Pool Details
        • liquidityPools()
        • isPoolValid()
        • isPoolStable()
        • tradingLiquidity()
        • depositingEnabled()
        • poolFundingLimit()
      • Trades
        • tradeOutputBySourceAmount()
        • tradeInputByTargetAmount()
        • tradingEnabled()
        • tradingFeePMM()
      • Withdrawals
        • isReadyForWithdrawal()
        • withdrawalRequest()
        • withdrawalAmounts()
        • withdrawalRequestIds()
        • withdrawalRequestCount()
        • lockDuration()
      • Pool Token Information
        • poolToken()
        • collectionByPool()
        • poolTokenToUnderlying()
        • underlyingToPoolToken()
      • Vortex
        • pendingNetworkFeeAmount()
        • minNetworkFeeBurn()
      • Surplus whitelist
        • protectedTokenWhitelist()
    • Data & Events
      • General Data
        • contextId
      • Trading Data
        • event TokensTraded()
      • Liquidity Data
        • TotalLiquidityUpdated()
        • TradingLiquidityUpdated()
        • TokensDeposited()
        • TokensWithdrawn()
        • WithdrawalInitiated()
        • WithdrawalCancelled()
        • WithdrawalCompleted()
        • LockDurationUpdated()
        • Cross AMM Migration Data
          • UniswapV2PositionMigrated()
          • SushiswapV1PositionMigrated()
      • Flashloan Data
        • FlashLoanCompleted()
        • FlashLoanFeePPMUpdated()
      • Rewards
        • Staking and Unstaking
          • Event ProviderJoined()
          • Event ProviderLeft()
        • Claiming and Restaking Rewards
          • Event RewardsClaimed()
          • Event RewardsStaked()
  • Developer Guides
    • Bancor Vortex Burner
    • Bancor Etherscan Guide
      • Etherscan Basics
      • Deposit
      • Deposit and Join
      • Rewards: Joining Standard Rewards
      • Rewards: Stake & Claim
      • Rewards: Leaving the Rewards Contract
      • Withdrawing Tokens
        • Initiating the Withdrawal
        • Completing the Withdrawal
      • Migrating V2.1 Positions
      • Rewards: Auto Compounding Rewards Distribution
    • REST API
      • API Reference
      • DLT Identifier
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  1. Contracts & Functions
  2. Write Functions

Transaction Prerequisites

Before interacting with a blockchain smart contract, you need approval

Before interacting with any blockchain smart contract, approval must be granted by the user for use of their tokens.

The options to grant approval include:

  • approve()

  • allowance()

PreviousWrite FunctionsNextapprove() / allowance()

Last updated 2 years ago