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Form: ModelValue

The modelValue or model can be considered as the ‘aorta’ of our form system. It is the single source of truth; not only for the current state of the form, also for all derived states: interaction, validation, visibility and other states are computed from a modelValue change.

Single source of truth

ModelValues are designed to provide the Application Developer a single way of programmatical interaction with the form for an Application Developer.

One single concept for Application Developers

Application Developers need to only care about interacting with the modelValue on a form control level, via:

  • .modelValue
  • @model-value-changed

Internal/private concepts like viewValue, formattedValue, serializedValue are therefore not recommended as a means of interaction.

For more information about parsing and the Unparseable type, see Formatting and Parsing

Event meta

model-value-changed events have a detail object, containing the following meta data:

  • isTriggeredByUser: a boolean that determines whether a change originated from a user or was triggered programmatically
  • formPath: an array of FormControls. It contains the path an event follows to go from a 'leaf element' (for instance a lion-input) to a top element (for instance lion-form). An example path could be [lionForm, lionFieldset, lionInput]
  • initialize: whether this is the first time the event is fired (on first render of the FormControl)