Operators should return a string

Author: Ryan Field

example.go

@@ -2,8 +2,9 @@ package goflow
 
 import (
 	"errors"
-	"log"
+	"fmt"
 	"math/rand"
+	"net/http"
 )
 
 // Crunch some numbers
@@ -14,6 +15,10 @@ func complexAnalyticsJob() *Job {
 		Active:   false,
 	}
 
+	j.AddTask(&Task{
+		Name:     "get-google",
+		Operator: Get{Client: &http.Client{}, URL: "https://google.com"},
+	})
 	j.AddTask(&Task{
 		Name:     "sleep-one",
 		Operator: Command{Cmd: "sleep", Args: []string{"1"}},
@@ -57,6 +62,7 @@ func complexAnalyticsJob() *Job {
 		TriggerRule: "allDone",
 	})
 
+	j.SetDownstream("get-google", "add-one-one")
 	j.SetDownstream("sleep-one", "add-one-one")
 	j.SetDownstream("add-one-one", "sleep-two")
 	j.SetDownstream("sleep-two", "add-two-four")
@@ -77,14 +83,14 @@ type randomFailure struct{ n int }
 var r = rand.New(rand.NewSource(1))
 
 // Run implements failures at random intervals.
-func (o randomFailure) Run(e *Execution) (any, error) {
+func (o randomFailure) Run(e *Execution) (string, error) {
 	x := r.Intn(o.n)
 
 	if x == o.n-1 {
-		return nil, errors.New("unlucky")
+		return "randomly failed", errors.New("unlucky")
 	}
 
-	return x, nil
+	return fmt.Sprintf("the result is %v", x), nil
 }
 
 func randomFailureJob() *Job {
@@ -100,7 +106,7 @@ type summation struct {
 }
 
 // Run performs summation.
-func (o summation) Run(e *Execution) (any, error) {
+func (o summation) Run(e *Execution) (string, error) {
 
 	result := o.Value
 
@@ -112,9 +118,7 @@ func (o summation) Run(e *Execution) (any, error) {
 		}
 	}
 
-	log.Printf("sum value=%v", result)
-
-	return result, nil
+	return fmt.Sprintf("sum value=%v", result), nil
 }
 
 func summationJob() *Job {

operator.go

@@ -10,7 +10,7 @@ import (
 // An Operator implements a Run() method. When a job executes a task that
 // uses the operator, the Run() method is called.
 type Operator interface {
-	Run(*Execution) (any, error)
+	Run(*Execution) (string, error)
 }
 
 // Command executes a shell command.
@@ -21,7 +21,7 @@ type Command struct {
 
 // Run passes the command and arguments to exec.Command and captures the
 // output.
-func (o Command) Run(e *Execution) (any, error) {
+func (o Command) Run(e *Execution) (string, error) {
 	out, err := exec.Command(o.Cmd, o.Args...).Output()
 	return string(out), err
 }
@@ -34,15 +34,15 @@ type Get struct {
 
 // Run sends the request and returns an error if the status code is
 // outside the 2xx range.
-func (o Get) Run(e *Execution) (any, error) {
+func (o Get) Run(e *Execution) (string, error) {
 	res, err := o.Client.Get(o.URL)
 	if err != nil {
-		return nil, err
+		return "", err
 	}
 	defer res.Body.Close()
 
 	if res.StatusCode < 200 || res.StatusCode > 299 {
-		return nil, fmt.Errorf("Received status code %v", res.StatusCode)
+		return "", fmt.Errorf("Received status code %v", res.StatusCode)
 	}
 
 	content, err := io.ReadAll(res.Body)
@@ -58,15 +58,15 @@ type Post struct {
 
 // Run sends the request and returns an error if the status code is
 // outside the 2xx range.
-func (o Post) Run(e *Execution) (any, error) {
+func (o Post) Run(e *Execution) (string, error) {
 	res, err := o.Client.Post(o.URL, "application/json", o.Body)
 	if err != nil {
-		return nil, err
+		return "", err
 	}
 	defer res.Body.Close()
 
 	if res.StatusCode < 200 || res.StatusCode > 299 {
-		return nil, fmt.Errorf("Received status code %v", res.StatusCode)
+		return "", fmt.Errorf("Received status code %v", res.StatusCode)
 	}
 
 	content, err := io.ReadAll(res.Body)