Callback props
Purpose
v0.1.6 adds function callback properties. Templates pass ordinary Go
function values through GX markup, and generated Go preserves those
expressions so the Go compiler checks the types.
Component Props
A component declares callback props in its props struct:
type ButtonProps struct {
OnClick func()
Children []gx.Node
}
The corresponding GX call passes the callback as a Go expression:
package notesui
import "github.com/busdk/bus-gx/pkg/gx"
func SaveButton(saveDraft func()) gx.Node {
return (
<Button onClick={saveDraft}>
Save draft
</Button>
)
}
The compiler lowers the callback expression into the props struct:
func SaveButton(saveDraft func()) gx.Node {
return Button(ButtonProps{
OnClick: saveDraft,
Children: []gx.Node{
gx.Text("Save draft"),
},
})
}
Callback props use the same attribute-to-field mapping as other component
props. onClick={saveDraft} maps to OnClick. A callback expression must be
assignable to the selected field type.
Element Props
Lowercase elements can also carry callback properties. This is how native browser elements expose callbacks to the frontend runtime:
package notesui
import "github.com/busdk/bus-gx/pkg/gx"
func SaveButton(saveDraft func()) gx.Node {
return (
<button class="primary" onClick={saveDraft}>
Save draft
</button>
)
}
The compiler lowers the element to a normal node with a function-valued property in Props:
func SaveButton(saveDraft func()) gx.Node {
return gx.Element("button", gx.Props{
"class": "primary",
"onClick": saveDraft,
}, gx.Text("Save draft"))
}
Element callback properties extend the v0.1.1 attribute-only
Props contract with runtime-only function values. The
native element surface is defined by intrinsic elements.
Function-valued element properties are retained in the render tree for runtimes and tests, but they are not serialized as HTML attributes by static HTML rendering.
Boundary
This patch defines how callback functions are represented and type checked in GX output. It does not define browser listener mounting, callback payload structs, a dispatch registry, or shared application behavior. Applications and component authors decide what each callback does in ordinary Go.
String values are not callback handlers. A callback prop such as
onClick={saveDraft} must not accept onClick="save-draft".