# Help Needed with Daml Trigger (Syntax related)

**URL:** <https://forum.canton.network/t/help-needed-with-daml-trigger-syntax-related/4441>\
**Category:** App Development\
**Tags:** trigger, damlhub\
**Created:** [April 27, 2022, 4:36pm UTC](https://forum.canton.network/t/help-needed-with-daml-trigger-syntax-related/4441 "2022-04-27T16:36:41Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![rikotacards](https://avatars.discourse-cdn.com/v4/letter/r/f0a364/32.png) [@rikotacards](https://forum.canton.network/u/rikotacards)\
**Post date:** [April 27, 2022, 4:36pm UTC](https://forum.canton.network/t/help-needed-with-daml-trigger-syntax-related/4441/1 "2022-04-27T16:36:41Z")

</div>

Currently, the below trigger exercises the choice “AssetHoldingAccountProposal\_Accept” for all incoming AssetHoldingAccountProposals. Upon accepting, the proposal gets archived, and the outstanding proposal contracts become a count of 0, and the trigger stops firing.

ISSUE:  
The issue is that, there will be the situation where the AssetHoldingAccountProposal CANNOT be accepted, becaues the user already has an existing AssetHoldingAccount.

WHAT I WANT TO DO:

- For incoming AssetHoldingAccountProposals, query the AssetHoldingAccount by key,
- if the result is not null (meaning there exists an assetHoldingAccount for this corresponding proposal)
- Reject the proposal (proposal gets archived)
- if null, accept the proposal (proposal gets archived)

This will stop the trigger from firing endlessly if I’m sending a proposal to someone that already has the account.

AssetHoldingAccountProposal Template

```haskell
template AssetHoldingAccountProposal with
    account : AssetHoldingAccount
    recipient : Party
  where
    signatory account.assetType.issuer
    observer recipient

    choice AssetHoldingAccountProposal_Accept : ContractId AssetHoldingAccount
      controller recipient 
      do
        create account with
          owner = recipient

    choice AssetHoldingAccountProposal_Reject : ()
      controller recipient 
      do
        return ()

```

CURRENT TRIGGER, (does not query AssetHoldingAccount)

```haskell
module AcceptAssetInviteTrigger where

import Account
import qualified Daml.Trigger as T
import DA.Foldable
import DA.Action

-- Auto accept assset invitation
acceptAssetInviteTrigger: T.Trigger ()
acceptAssetInviteTrigger = T.Trigger 
 { initialize = pure (),
  updateState = \_ -> pure (),
  registeredTemplates = T.RegisteredTemplates [T.registeredTemplate @AssetHoldingAccountProposal],
  rule = \p -> do
    requests <- T.query @AssetHoldingAccountProposal
    let isMe = (\requests -> requests.recipient == p)
    let meList = filter (\(_, contract) -> isMe contract) requests
    let requests = map fst meList

    debug ("asset holding account invites", requests)

    
    unless ( DA.Foldable.null requests ) do
       mapA_ (\request -> T.dedupExercise request AssetHoldingAccountProposal_Accept) requests
      
    debug $ "TRIGGERED",
  heartbeat = None
}

```

I’m trying to do something like the below

```haskell
module AcceptAssetInviteTrigger where

import Account
import qualified Daml.Trigger as T
import DA.Foldable
import DA.Action
import DA.Optional (isSome, whenSome)

-- Auto accept assset invitation
acceptAssetInviteTrigger: T.Trigger ()
acceptAssetInviteTrigger = T.Trigger 
 { initialize = pure (),
  updateState = \_ -> pure (),
  registeredTemplates = T.RegisteredTemplates [T.registeredTemplate @AssetHoldingAccountProposal, T.registeredTemplate @AssetHoldingAccount],
  rule = \p -> do
    requests <- T.query @AssetHoldingAccountProposal
    let isMe = (\requests -> requests.recipient == p)
    let meList = filter (\(_, contract) -> isMe contract) requests
    let requests = meList

    debug ("asset holding account invites", requests)

    
    unless ( DA.Foldable.null requests ) do
      case requests of 
        [] -> pure()
        (requestCid, c) :: _ -> do
          optAccount <- T.queryContractKey @AssetHoldingAccount (c.account.assetType, c.account.owner)
          if isSome(optAccount) 
            then do 
              T.dedupExercise requestCid AssetHoldingAccountCloseProposal_Reject
          else do 
            T.dedupExercise requestCid AssetHoldingAccountProposal_Accept
      
    debug $ "TRIGGERED",
  heartbeat = None
}

```

and I get a red squiggle under the first T.dedupExercise, right below the `then do` line. Saying

• No instance for (HasExercise  
AssetHoldingAccountProposal  
AssetHoldingAccountCloseProposal\_Reject  
r0)  
arising from a use of ‘T.dedupExercise’

I’m not sure what the right syntax to use is, I need to map through the incoming requests,  
Then query the @AssetHoldingAccount, and then if its NOT null, I need to reject the proposal requests.

---

<div class="post-metadata">

**Author:** ![cocreature](https://yyz2.discourse-cdn.com/flex034/user_avatar/forum.canton.network/cocreature/32/36_2.png) [@cocreature](https://forum.canton.network/u/cocreature)\
**Post date:** [April 27, 2022, 5:45pm UTC](https://forum.canton.network/t/help-needed-with-daml-trigger-syntax-related/4441/2 "2022-04-27T17:45:22Z")

</div>

It looks like you typoed your choice name. Your trigger is calling `AssetHoldingAccountCloseProposal_Reject` but the choice is called `AssetHoldingAccountProposal_Reject` without the `Close`.

---

<div class="post-metadata">

**Author:** ![rikotacards](https://avatars.discourse-cdn.com/v4/letter/r/f0a364/32.png) [@rikotacards](https://forum.canton.network/u/rikotacards)\
**Post date:** [April 27, 2022, 6:06pm UTC](https://forum.canton.network/t/help-needed-with-daml-trigger-syntax-related/4441/3 "2022-04-27T18:06:39Z")

</div>

> [@rikotacards](#):
>
> ```haskell
> module AcceptAssetInviteTrigger where
> 
> import Account
> import qualified Daml.Trigger as T
> import DA.Foldable
> import DA.Action
> import DA.Optional (isSome, whenSome)
> 
> -- Auto accept assset invitation
> acceptAssetInviteTrigger: T.Trigger ()
> acceptAssetInviteTrigger = T.Trigger 
> { initialize = pure (),
> updateState = \_ -> pure (),
> registeredTemplates = T.RegisteredTemplates [T.registeredTemplate @AssetHoldingAccountProposal, T.registeredTemplate @AssetHoldingAccount],
> rule = \p -> do
> requests <- T.query @AssetHoldingAccountProposal
> let isMe = (\requests -> requests.recipient == p)
> let meList = filter (\(_, contract) -> isMe contract) requests
> let requests = meList
> 
> debug ("asset holding account invites", requests)
> 
>     
> unless ( DA.Foldable.null requests ) do
> case requests of 
> [] -> pure()
> (requestCid, c) :: _ -> do
> optAccount <- T.queryContractKey @AssetHoldingAccount (c.account.assetType, c.account.owner)
> if isSome(optAccount) 
> then do 
> T.dedupExercise requestCid AssetHoldingAccountCloseProposal_Reject
> else do 
> T.dedupExercise requestCid AssetHoldingAccountProposal_Accept
>       
> debug $ "TRIGGERED",
> heartbeat = None
> }
> 
> ```

… And that fixed it. Thank you!