Define a Simple Currency Component

Interface patterns give you an opportunity to explore different interface designs. To learn how to directly use patterns within your interfaces, see How to Adapt a Pattern for Your Application.

Goal

Show a text field that allows the user to enter dollar amounts including the dollar symbol and thousand separators, but save the value as a decimal rather than text. Additionally, always show the dollar amount with the dollar symbol.

This design pattern is not recommended for offline interfaces because reflecting immediate changes in an interface based on user interaction requires a connection to the server.

This scenario demonstrates:

  • How to configure an interface component to format a user's input

Expression

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=load(
  local!amount,
  a!textField(
    label:"Amount in Text",
    /* Instructions  show the saved datatype*/
    instructions: "Type of local!amount: " & typename(typeof(local!amount)),
    value: if(isnull(local!amount), "", dollar(local!amount)),
    /* Instead of saving the value as text, a!save() is used to store to the desired datatype*/
    saveInto: a!save(local!amount, todecimal(save!value))
  )
)

Test it out

  1. Enter $12345 and click away from the field. Notice that the text box shows $12,345.00 and that the saved value is a decimal.
  2. Enter $12,345.23 and click away from the field.
  3. Enter a1b2c3 and click away. Notice that the text box removes the non-numeric characters and treats the remaining as a decimal value. A true currency component would catch this as an error case, hence why this is called a simple currency example.

Notable Implementation Details

  • Because dollar() will not accept a null value, we set the value conditionally until local!amount has a value
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