Web3.Transaction

Transaction lifecycle state machine.

Every transaction goes through explicit states. Pattern matching forces you to handle every case — no "transaction failed silently" bugs.

case tx.status of
    Idle ->
        viewBuyButton


    AwaitingSignature ->
        viewSigningSpinner


    Submitted hash ->
        viewPendingWithHash hash


    Confirmed receipt ->
        viewSuccess receipt


    Failed err ->
        viewError err

type Status

= Idle

| AwaitingSignature

| Submitted TxHash

| Confirming TxHash Int

| Confirmed Receipt

| Failed String

| Rejected

Transaction lifecycle status. Cannot be in an invalid state.

type Msg

= TxSubmitted String

| TxConfirmation String Int

| TxConfirmed ReceiptJson

| TxFailed String

| TxRejected

Messages from the JS transaction port.

type alias Receipt =

{ txHash : TxHash

, blockNumber : Int

, gasUsed : String

, status : Bool

, logs : List EventLog

}

A confirmed transaction receipt, including emitted logs.

type alias EventLog =

{ address : Address

, topics : List String

, data : String

, blockNumber : Int

, logIndex : Int

}

A single log entry emitted during a transaction.

update : Msg -> Status -> Status

Update transaction status from a port message.

Transitions are guarded to match the TLA+ GuardedNext specification:

Terminal states (Confirmed, Failed, Rejected) never transition out.
TxSubmitted is only accepted from AwaitingSignature.
TxConfirmation is only accepted from Submitted or Confirming.
TxFailed and TxRejected are accepted from any non-terminal state.

isTerminal : Status -> Bool

Is this status terminal (no more updates expected)?

isPending : Status -> Bool

Is this status still pending?

decoder : Decoder Msg

Decode transaction messages from JS port.

parseReceiptEvents : List (EventLog -> Maybe a) -> Receipt -> List a

Apply a list of event decoders to the logs in a receipt, collecting all successfully decoded events.

type MyEvent
    = Transfer { from : Address, to : Address, amount : BigInt }
    | Approval { owner : Address, spender : Address, amount : BigInt }


decodeTransfer : EventLog -> Maybe MyEvent
decodeTransfer log =
    -- match topic[0] to Transfer signature, then decode
    ...


events : List MyEvent
events =
    parseReceiptEvents [ decodeTransfer, decodeApproval ] receipt

quietgarden/elm-web3/1.0.0

Web3.Transaction

Modules