Ergo-Native Features
Intermediate
4-8 hoursCrowdfunding / Assurance Contract Pattern
On-chain crowdfunding where contributors are refunded if target is not reached
Problem
You want to raise funds for a project, but contributors need assurance they'll get refunds if the goal isn't met.
Lösung
Assurance contracts collect contributions into a shared box. If the funding goal is reached before deadline, funds go to the project. Otherwise, contributors can claim refunds.
Funktionsweise
- 1Project creates campaign box with goal, deadline, and recipient
- 2Contributors add funds to campaign (tracked via tokens or registers)
- 3Each contribution creates a refund token for the contributor
- 4If goal reached: recipient can claim all funds
- 5If deadline passes without goal: contributors claim refunds with tokens
- 6Refund tokens are burned on claim
Code-Beispiele
{
// Crowdfunding campaign box
// R4: Funding goal (nanoERG)
// R5: Deadline (block height)
// R6: Project recipient address
// R7: Refund token ID
val fundingGoal = SELF.R4[Long].get
val deadline = SELF.R5[Int].get
val recipient = SELF.R6[Coll[Byte]].get
val refundTokenId = SELF.R7[Coll[Byte]].get
val currentFunds = SELF.value
val goalReached = currentFunds >= fundingGoal
val deadlinePassed = HEIGHT > deadline
// Success: goal reached, recipient claims
val successClaim = {
goalReached &&
OUTPUTS(0).propositionBytes == recipient &&
OUTPUTS(0).value >= fundingGoal
}
// Add contribution (before deadline)
val addContribution = {
!deadlinePassed &&
OUTPUTS(0).propositionBytes == SELF.propositionBytes &&
OUTPUTS(0).value > SELF.value &&
OUTPUTS(0).R4[Long].get == fundingGoal &&
OUTPUTS(0).R5[Int].get == deadline
}
// Refund claim (deadline passed, goal not reached)
val refundClaim = {
deadlinePassed && !goalReached &&
// Refund token burned in this transaction
INPUTS.exists(i =>
i.tokens.exists(t => t._1 == refundTokenId)
)
}
successClaim || addContribution || refundClaim
}Campaign box that accepts contributions, allows success claim if goal met, or refunds if deadline passes.
Anwendungsfälle
- →Project fundraising
- →Community initiatives
- →Charity campaigns
- →Product pre-orders
- →DAO treasury bootstrapping
Sicherheitshinweise
- !Set realistic deadlines and goals
- !Test refund mechanism thoroughly
- !Consider partial funding scenarios
- !Protect against griefing attacks
- !Audit token minting and burning logic
Ressourcen
Gebührenhinweise
Contributors pay for contribution tx. Refund claims also require fees. Consider fee reserves.