VelaCtx — Runtime Context

defkit.VelaCtx() returns a KubeVela context accessor that compiles to CUE context.* references, evaluated by the controller at deploy time.

defkit.VelaCtx() *VelaContext

Call at the top of your template function or definition constructor. Each method returns a Value that produces the corresponding context.* CUE path.

Go — defkit

vela := defkit.VelaCtx()

vela.Name()                    // component name
vela.AppName()                 // application name
vela.Namespace()               // namespace
vela.Revision()                // revision name
vela.ClusterVersion().Minor()  // cluster minor version (int)

CUE — generated

vela.Name()                   → context.name
vela.AppName()                → context.appName
vela.Namespace()              → context.namespace
vela.Revision()               → context.revision
vela.ClusterVersion().Minor() → context.clusterVersion.minor

Context Fields Reference

Go method	CUE path	Description
vela.Name()	context.name	Component instance name
vela.AppName()	context.appName	Parent Application name
vela.Namespace()	context.namespace	Deployment namespace
vela.Revision()	context.revision	App revision string
vela.ClusterVersion().Minor()	context.clusterVersion.minor	Kubernetes minor version (int)

Usage in Resource Fields

The most common use of VelaCtx is setting metadata on generated resources:

Go — defkit

vela := defkit.VelaCtx()

resource := defkit.NewResource("apps/v1", "Deployment").
    Set("metadata.name", vela.Name()).
    Set("metadata.namespace", vela.Namespace()).
    Set("metadata.labels[app.oam.dev/name]", vela.AppName()).
    Set("metadata.labels[app.oam.dev/component]", vela.Name())

CUE — generated

metadata: {
    name:      context.name
    namespace: context.namespace
    labels: {
        "app.oam.dev/name":      context.appName
        "app.oam.dev/component": context.name
    }
}

Usage in Conditions and Comparisons

Context values can be used in comparison expressions for runtime-conditional behaviour:

Go — defkit

vela := defkit.VelaCtx()

hpa := defkit.NewResourceWithConditionalVersion("HorizontalPodAutoscaler").
    VersionIf(defkit.Lt(vela.ClusterVersion().Minor(), defkit.Lit(23)), "autoscaling/v2beta2").
    VersionIf(defkit.Ge(vela.ClusterVersion().Minor(), defkit.Lit(23)), "autoscaling/v2").
    Set("metadata.name", vela.Name())

CUE — generated

apiVersion: {
    if context.clusterVersion.minor < 23 { "autoscaling/v2beta2" }
    if context.clusterVersion.minor >= 23 { "autoscaling/v2" }
}
kind: "HorizontalPodAutoscaler"
metadata: name: context.name

Usage in String Interpolation

Context values integrate naturally with defkit.Interpolation():

Go — defkit

vela := defkit.VelaCtx()
name := defkit.String("name")

clusterScopedName := defkit.Interpolation(
    vela.Namespace(),
    defkit.Lit("/"),
    name,
)

CUE — generated

"\(context.namespace)/\(parameter.name)"

Reading Component Output in Traits

Traits can inspect the component's output resource using defkit.ContextOutput():

Go — defkit

ref := defkit.ContextOutput()

templateRef := defkit.ContextOutput().Field("spec.template")

hasTemplate := defkit.ContextOutput().HasPath("spec.template")

patch := defkit.NewPatchResource()
patch.If(hasTemplate).
    Set("spec.template.metadata.labels.app", defkit.Lit("test")).
    EndIf()

CUE — generated

// .HasPath("spec.template")
context.output.spec.template != _|_

// .Field("spec.template")
context.output.spec.template

info

All VelaCtx methods return Value objects — they are not evaluated in Go. The actual values are substituted by the KubeVela controller at deploy time when the CUE template is executed against the Application spec.