Tutorial: Add a new feature with UI elements to your Daml app. Code Error

Questions
1

Good Day, I am following the Second tutorial instructions and I got this error in the DAML code
I don’t know what I am doing wrong

image
image1862×881 109 KB

the error is this

image
image1874×839 111 KB

it is not very clear which code I should reeplace

2 Likes
2

Hi @lisandro_iraguen,

the SendMessage choice should be a choice on the User template not on Message. In your example, that means moving it above the definition of Message in line 30. The final state should look something like the following:

-- MAIN_TEMPLATE_BEGIN
template User with
    username: Party
    following: [Party]
  where
    signatory username
    observer following
-- MAIN_TEMPLATE_END

    key username: Party
    maintainer key

    -- FOLLOW_BEGIN
    nonconsuming choice Follow: ContractId User with
        userToFollow: Party
      controller username
      do
        assertMsg "You cannot follow yourself" (userToFollow /= username)
        assertMsg "You cannot follow the same user twice" (notElem userToFollow following)
        archive self
        create this with following = userToFollow :: following
    -- FOLLOW_END
    nonconsuming choice SendMessage: ContractId Message with
        sender: Party
        content: Text
      controller sender
      do
        assertMsg "Designated user must follow you back to send a message" (elem sender following)
        create Message with sender, receiver = username, content

template Message with
    sender: Party
    receiver: Party
    content: Text
  where
    signatory sender, receiver
3 Likes
3

At the bottom of the tutorial UI pane it says (paraphrase) that the ‘sendmessage’ choice should be in/on the same indentation or alignment of the ‘follow’. Is that correct?

It is not easy to see the alignments on those screenshots.

1 Like
4

thank you so much for your reply, I can understand now what was wrong >D

1 Like
5

Hi, just another tip to help the forum members help you.

Perhaps when you display code in a UI Pane like you did, you can grab the central vertical slider and move it horizontally to the right. That way you can expand the UI Pane out and the tutorial code is displayed visually as it should be written. Now, take a screenshot.

Then grab the central vertical slider and slide it to the left, until the code in the code viewer UI is displayed visually, as it should be written (Except for very long lines). Now take a screenshot.

Post the tutorial instructions first, followed by the code viewer screenshot. That way we get the best view at your issue.

See the following screenshot where I have highlighted the vertical.

Adjust_UI_Pane_Using_Mouse
Adjust_UI_Pane_Using_Mouse1142×732 84.9 KB

Hope this helps :+1:t2:

3 Likes
6

An even better option is to copy the code and format it in a code block instead of using a screenshot. That way people can reproduce the issue much easier, the code becomes searchable and it’s more accessible.

To use a code block simply wrap your code in triple backticks.

3 Likes
7

OK, @cocreature 1, @quidagis 0 :joy:

1 Like