PropertyLoadSaver for struct with slice and map example?

[nvcnvn]

for example:

type Bar struct {
  X, Y int64
}
type Foo struct {
  Additional map[string]string
  Bar []Bar
}

Because of the map[string]string I need to use PropertyLoadSaver interface, the map is handled simple but I got some trouble with the slice of Bar. I hope someone can show me the example how to handle slice of struct.

Bellow is my code:

func (f *Foo) Load(c <-chan datastore.Property) error {
  for p := range c {
    if strings.HasPrefix(p.Name, "Additional.") {
      f.Additional[p.Name[11:]] = string(p.Value)
    }
  }
  return nil
}
func (f *Foo) Save(c chan<- datastore.Property) error {
  defer close(c)
  for key, val :=range f.Additional {
    c <- datastore.Property{
      Name:  "Additional."+key,
      Value: val,
    }
  }
  return nil
}

[Glenn Lewis]

Here is a completely wild shot-in-the-dark, as I have not used the PropertyLoadSaver yet in my apps.

So take this with a grain of salt, and maybe someone with more experience will reply with their nicer solution.

(I think I may have got the type assertions wrong, but you can figure that out with the compiler.)

I hope this helps.

-- Glenn

import (

"fmt"

"regexp"

"strconv"

"strings"

"appengine/datastore"

)

type Bar struct {

X, Y int64

}

type Foo struct {

Additional map[string]string

Bar        []Bar

}

func (f *Foo) Load(c <-chan datastore.Property) error {

barRE := regexp.MustCompile(`^Bar\.(\d+)\.(\d+).([XY])$`)

for p := range c {

if strings.HasPrefix(p.Name, "Additional.") {

f.Additional[p.Name[11:]] = string(p.Value)

}

if m := barRE.FindStringSubmatch(p.Name); m != nil {

size, err := strconv.Atoi(m[1])

if err != nil {

return err

}

i, err := strconv.Atoi(m[2])

if err != nil {

return err

}

if f.Bar == nil {

f.Bar = make([]Bar, size)

}

switch m[3] {

case "X":

f.Bar[i].X = int64(p.Value)

case "Y":

f.Bar[i].Y = int64(p.Value)

}

}

}

return nil

}

func (f *Foo) Save(c chan<- datastore.Property) error {

defer close(c)

for key, val := range f.Additional {

c <- datastore.Property{

Name:  "Additional." + key,

Value: val,

}

}

for i, val := range f.Bar {

c <- datastore.Property{

Name:  fmt.Sprintf("Bar.%d.%d.X", len(f.Bar), i),

Value: val.X,

}

c <- datastore.Property{

Name:  fmt.Sprintf("Bar.%d.%d.Y", len(f.Bar), i),

Value: val.Y,

}

}

return nil

}

[nvcnvn]

Hi Glenn, thanks for you solution :)

But after rereading the datastore package referrence I found the solution of appengine is turn a slice of struct into some slice.

[Glenn Lewis]

Cool! I am glad you found the answer.
If you wouldn't mind sharing an updated example on this list, that would be great.
Thanks!

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[Nguyễn Văn Cao Nguyên]

(I get some trouble with replying using group web interface)

I just write down and test the code a litle, here is my implement

func (f *Foo) Load(c <-chan datastore.Property) error {

f.Additional = make(map[string]string)
f.Bar = make([]Bar, 0, 2) // somehow to know the length?
countBar := 0

for p := range c {
if strings.HasPrefix(p.Name, "Additional.") {

f.Additional[p.Name[11:]] = p.Value.(string)
} else if p.Name == "Bar.X" {
f.Bar = append(f.Bar, Bar{X: p.Value.(int64)})
} else if p.Name == "Bar.Y" {
f.Bar[countBar].Y = p.Value.(int64)
countBar++

}
}
return nil
}
func (f *Foo) Save(c chan<- datastore.Property) error {
defer close(c)

for i := 0; i < len(f.Bar); i++ {
c <- datastore.Property{
Name:     "Bar.X",
Value:    int64(f.Bar[i].X),
Multiple: true,
}
c <- datastore.Property{
Name:     "Bar.Y",
Value:    int64(f.Bar[i].Y),
Multiple: true,

}
}
for key, val := range f.Additional {
c <- datastore.Property{
Name:  "Additional." + key,
Value: val,
}
}

return nil
}

Here is an full application: http://play.golang.org/p/5vrBqE_VOf 

--

Nguyễn Văn Cao Nguyên

    /**

     * Contact : +84+935704595

     * Blog      :  http://nguyen.open-vn.org

     */