5aed8b3ef5
Functions must be annotated as `stateful` in order to - Update the contract state (using `put`) - Call `Chain.spend` or other primitive functions that cost tokens - Call an Oracle or AENS function that requires a signature - Make a remote call with a non-zero value - Construct a lambda calling a stateful function It does not need to be stateful to - Read the contract state - Call another contract with value=0, even when the remote function is stateful
66 lines
2.1 KiB
Plaintext
66 lines
2.1 KiB
Plaintext
/*
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* A simple crowd-funding example
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*/
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contract FundMe =
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record spend_args = { recipient : address,
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amount : int }
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record state = { contributions : map(address, int),
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total : int,
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beneficiary : address,
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deadline : int,
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goal : int }
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private function require(b : bool, err : string) =
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if(!b) abort(err)
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private stateful function spend(args : spend_args) =
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Chain.spend(args.recipient, args.amount)
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public function init(beneficiary, deadline, goal) : state =
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{ contributions = {},
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beneficiary = beneficiary,
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deadline = deadline,
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total = 0,
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goal = goal }
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private function is_contributor(addr) =
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Map.member(addr, state.contributions)
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public stateful function contribute() =
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if(Chain.block_height >= state.deadline)
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spend({ recipient = Call.caller, amount = Call.value }) // Refund money
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false
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else
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let amount =
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Map.lookup_default(Call.caller, state.contributions, 0) + Call.value
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put(state{ contributions[Call.caller] = amount,
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total @ tot = tot + Call.value })
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true
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public stateful function withdraw() =
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if(Chain.block_height < state.deadline)
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abort("Cannot withdraw before deadline")
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if(Call.caller == state.beneficiary)
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withdraw_beneficiary()
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elif(is_contributor(Call.caller))
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withdraw_contributor()
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else
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abort("Not a contributor or beneficiary")
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private stateful function withdraw_beneficiary() =
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require(state.total >= state.goal, "Project was not funded")
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spend({recipient = state.beneficiary,
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amount = Contract.balance })
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put(state{ beneficiary = ak_11111111111111111111111111111111273Yts })
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private stateful function withdraw_contributor() =
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if(state.total >= state.goal)
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abort("Project was funded")
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let to = Call.caller
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spend({recipient = to,
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amount = state.contributions[to]})
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put(state{ contributions @ c = Map.delete(to, c) })
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