tick

Documentation

Overview

TICKscript is a simple invocation chaining DSL.

See the examples for how its used and example syntax of the DSL.

Index

• Variables
• func Evaluate(script string, scope *stateful.Scope, predefinedVars map[string]Var, ...) (_ map[string]Var, err error)
• func Format(script string) (string, error)
• type PartialDescriber
• type ReflectionDescriber
  • func NewReflectionDescriber(obj interface{}, chainMethods map[string]reflect.Value) (*ReflectionDescriber, error)
  • func (r *ReflectionDescriber) CallChainMethod(name string, args ...interface{}) (interface{}, error)
  • func (r *ReflectionDescriber) Desc() string
  • func (r *ReflectionDescriber) HasChainMethod(name string) bool
  • func (r *ReflectionDescriber) HasProperty(name string) bool
  • func (r *ReflectionDescriber) Property(name string) interface{}
  • func (r *ReflectionDescriber) SetProperty(name string, values ...interface{}) (interface{}, error)
• type SelfDescriber
• type Var

Examples

• Evaluate

Variables

var ErrEmptyStack = errors.New("stack is empty")

Functions

func Evaluate

func Evaluate(script string, scope *stateful.Scope, predefinedVars map[string]Var, ignoreMissingVars bool) (_ map[string]Var, err error)

Parse and evaluate a given script for the scope. Returns a set of default vars. If a set of predefined vars is provided, they may effect the default var values.

Example

package main

import (
	"fmt"

	"github.com/influxdata/kapacitor/tick/stateful"
)

type Process struct {
	Name     string
	Children []*Process
}

func (p *Process) Spawn() *Process {
	child := &Process{}
	p.Children = append(p.Children, child)
	return child
}

func (p *Process) String() string {
	return fmt.Sprintf("{%q %s}", p.Name, p.Children)
}

func main() {

	//Run a test that evaluates the DSL against the Process struct.
	script := `
//Name the parent
parent.name('parent')

// Spawn a first child
var child1 = parent|spawn()

// Name the first child
child1.name('child1')

//Spawn a grandchild and name it
child1|spawn().name('grandchild')

//Spawn a second child and name it
parent|spawn().name('child2')
`

	scope := stateful.NewScope()
	parent := &Process{}
	scope.Set("parent", parent)

	_, err := Evaluate(script, scope, nil, false)
	if err != nil {
		fmt.Println(err)
	}

	fmt.Println(parent)
}

Output:

{"parent" [{"child1" [{"grandchild" []}]} {"child2" []}]}

func Format

func Format(script string) (string, error)

Formats a TICKscript according to the standard.

Types

type PartialDescriber

type PartialDescriber interface {
	ChainMethods() map[string]reflect.Value
}

PartialDescriber can provide a description of its chain methods that hide embedded property methods.

type ReflectionDescriber

type ReflectionDescriber struct {
	// contains filtered or unexported fields
}

Wraps any object as a SelfDescriber using reflection.

Uses tags on fields to determine if a method is really a PropertyMethod Can disambiguate property fields and chain methods of the same name but from different composed anonymous fields. Cannot disambiguate property methods and chain methods of the same name. See NewReflectionDescriber for providing explicit chain methods in this case.

Example:

type MyType struct {
    UseX `tick:"X"`
}
func (m *MyType) X() *MyType{
    m.UseX = true
    return m
}

UseX will be ignored as a property and the method X will become a property method.

Expects that all callable methods are pointer receiver methods.

func NewReflectionDescriber

func NewReflectionDescriber(obj interface{}, chainMethods map[string]reflect.Value) (*ReflectionDescriber, error)

Create a NewReflectionDescriber from an object. The object must be a pointer type. Use the chainMethods parameter to provide a set of explicit methods that should be considered chain methods even if an embedded type declares them as property methods

Example:

type MyType struct {
    UseX `tick:"X"`
}
func (m *MyType) X() *MyType{
    m.UseX = true
    return m
}

type AnotherType struct {
    MyType
}
func (a *AnotherType) X() *YetAnotherType {
    // do chain method work here...
}

// Now create NewReflectionDescriber with X as a chain method and property method
at := new(AnotherType)
rd := NewReflectionDescriber(at, map[string]reflect.Value{
    "X": reflect.ValueOf(at.X),
})
rd.HasProperty("x") // true
rd.HasChainMethod("x") // true

func (*ReflectionDescriber) CallChainMethod

func (r *ReflectionDescriber) CallChainMethod(name string, args ...interface{}) (interface{}, error)

func (*ReflectionDescriber) Desc

func (r *ReflectionDescriber) Desc() string

func (*ReflectionDescriber) HasChainMethod

func (r *ReflectionDescriber) HasChainMethod(name string) bool

Using reflection check if the object has the method or field. A field is a valid method because we can set it via reflection too.

func (*ReflectionDescriber) HasProperty

func (r *ReflectionDescriber) HasProperty(name string) bool

Using reflection check if the object has a field with the property name.

func (*ReflectionDescriber) Property

func (r *ReflectionDescriber) Property(name string) interface{}

func (*ReflectionDescriber) SetProperty

func (r *ReflectionDescriber) SetProperty(name string, values ...interface{}) (interface{}, error)

type SelfDescriber

type SelfDescriber interface {
	//A description the object
	Desc() string

	HasChainMethod(name string) bool
	CallChainMethod(name string, args ...interface{}) (interface{}, error)

	HasProperty(name string) bool
	Property(name string) interface{}
	SetProperty(name string, args ...interface{}) (interface{}, error)
}

Interface for interacting with objects. If an object does not self describe via this interface than a reflection based implemenation will be used.

type Var

type Var struct {
	Value       interface{}
	Type        ast.ValueType
	Description string
}