Data binding

Data binding

Data / Resources / Inputs / Results / Children / Size / State
        │
        ▼
   Binding Path / MultiBinding Paths
        │
        ▼
   Converter (optional)
        │
        ▼
   Text / Button / Image / TextBox / ...

Two forms

Shorthand

<Text Value="{Data.News.Title}" />
<Text Value="Hello {Inputs.Name}" />
<Text Value="{Inputs.Age}" />

• {path} is the interpolation marker.
• A string containing only one binding preserves the original type (number, boolean, object, array).
• Mixed text is converted to a string.
• A missing path yields an empty string.

Explicit Binding

<Text Value="{Binding Data.News.Title}" />
<Text Value="{Binding Data.News.Title, Converter=Upper}" />
<TextBox Value="{Binding Inputs.Price, Converter=Money, Mode=TwoWay}" />

<Text Value="{Binding Inputs.Name, Converter=Format, ConverterParameter='N2'}" />

Path syntax

Data.News.Items.0.Title
Resources.AppName
Inputs.Keyword
Results.Search.Items.1.Name
Children.Weather.Data.Temp
Size.PixelWidth
State.Loading

• Paths are case-sensitive: {data.Title} differs from {Data.Title}.
• Array indexes must be decimal: Items.0.
• Only own object properties are readable; constructor, prototype, and __proto__ are blocked.
• A missing path, type mismatch, or unloaded source yields an empty value.
• Property names cannot contain dots; use nested objects instead.

Namespaces

Data

<Data Name="News" Type="Json" Url="https://api.example.com/news" />
<Data Type="Json" Url="https://api.example.com/default" />

• Named source: {Data.News.Title}, or directly {News.Title}.
• An unnamed source defaults to Data; its fields merge into {Data.Title}.
• Duplicate data source names are rejected by XML validation.
• Data.Status.News: Loading / Completed / Error.
• With Async="True", the widget renders first and bindings refresh after loading.

Resources

<Resources>
  <String Name="AppName">Qomicex</String>
  <Bool Name="ShowTip">True</Bool>
  <Number Name="PageSize">10</Number>
  <Binary Name="Beep" Mime="audio/wav">BASE64...</Binary>
</Resources>

<Text Value="{Resources.AppName}" />

Results

Children

<Widget.Using Name="Weather" As="Weather" />
<Text Value="{Children.Weather.Data.Temp}" />
<Text Value="{Children.Weather.Outputs.Summary}" />

Size and State

<Text Value="{Size.Width} × {Size.Height}" />
<Text Value="{Size.PixelWidth}px" />
<If Test="{State.Error}">
  <Text Value="Loading failed" Color="Destructive" />
</If>

Type rules

<Button.Arguments><![CDATA[{"age":"{Inputs.Age}","tags":"{Data.Tags}"}]]></Button.Arguments>
<Select Options="{Data.Options}" />
<List Items="{Data.Items}" />

Converter

<Widget.Converters>
  <Converter Name="Upper" Type="Upper" />
  <Converter Name="Money" Type="Format" Format="N2" />
  <Converter Name="Visible" Type="BoolToVisibility" />
  <Converter Name="Label" Type="Map">
    <MapEntry From="True" To="On" />
    <MapEntry From="False" To="Off" />
  </Converter>
</Widget.Converters>

<Text Value="{Binding Data.News.Title, Converter=Upper}" />
<TextBox Value="{Binding Inputs.Price, Converter=Money, Mode=TwoWay}" />

ConverterParameter

<Text Value="{Binding Inputs.Price, Converter=Money, ConverterParameter='N0'}" />

ConvertBack

• TextBox
• CheckBox
• Slider

MultiBinding

<Text Value="{MultiBinding Paths='Inputs.First|Inputs.Last', Converter=Join, ConverterParameter=' '}" />

• Paths is separated by |.
• Multi-value converters receive a values array.
• Join joins all values.
• Current input controls write MultiBinding changes only to the first path.

Bindings in action parameters

<Button Text="Open" OnClick="OpenUrl" Url="{Data.Link}" />
<Button Text="Save" OnClick="CallFunction" Function="Save">
  <Button.Arguments><![CDATA[{"name":"{Inputs.Name}","age":18}]]></Button.Arguments>
</Button>

List scope

<List Items="{Data.Items}" As="Item">
  <ListItem>
    <Text Value="{Item.Title}" />
    <Text Value="{Index}" />
  </ListItem>
</List>

• {Item.*}: current item; the variable name comes from As.
• {Index}: 0-based current item index.
• Nested lists shadow Item / Index.
• List.Items must be an array; an object renders an empty list.

Refresh and lifecycle

• Bindings recompute with the latest scope after data changes.
• Async="True" does not block first paint; bindings refresh after loading.
• Data.Status.* supports loading and error placeholders.
• Remote updates confirm only executable-content changes; ordinary data/text/layout changes are silent.

Editor support

• Typing { completes Data / Resources / Inputs / Results / Children / Size / State.
• Typing {Binding completes paths.
• Converter= completes converter names defined in the current XML.
• Converter names and ConverterParameter are validated during XML parsing.

Common mistakes

• Path case is significant: {data.Title} differs from {Data.Title}.
• Bindings are empty while data loads; use If Test="{State.Loading}" for a placeholder.
• Static Data.Url / Data.Path do not support runtime binding; use {Inputs.*} for dynamic sources.
• A misspelled converter fails parsing with unknown Converter.
• OneWay controls do not write back; declare Mode="TwoWay" for two-way inputs.
• MultiBinding Paths uses |, not commas.
• Script converters run synchronously and must not perform network I/O; remote scripts require executable confirmation.

Limits

• Paths only read object properties; no method calls, expressions, or indexer syntax.
• Bindings evaluate synchronously; converters must not perform I/O or heavy work.
• Static Data.Url does not participate in runtime binding; dynamic sources use limited Inputs / Data forms.
• Raw < in XML attributes must be written as <.
• There is no Binding.DoNothing; return undefined from ConvertBack to skip a write-back.