Support one to many mappings with slices

[hermanschaaf]

As best I can tell, it is currently not possible to use goverter to map the Input to the Output in this case:

package example

// goverter:converter
type Converter interface {
    Convert(Input) (Output, error)
}

type Input struct {
    Envs []Env
}
type Env struct {
    Key string
    Value string
}
type Output struct {
    EnvKeys []string
    EnvValues []string
}

Is there a known solution to this?

If not, one solution I would like to suggest is a post-hook function where the user can receive the Input and Output structs and make any final alterations to it, if necessary.

[jmattheis]

If it's an simple example it could define the complete conversion function yourself via extend otherwise there are two ways to do this with generation support.

1. Via default, this works similar to a before hook. It normally is used to instantiate the type. Here you have to ignore the already defined fields.

   // goverter:converter
   type ConverterWithDefault interface {
      // goverter:default PreProcess
      // goverter:ignore EnvKeys EnvValues
      Convert(Input) (Output, error)
   }

2. Via map [SOURCE-PATH] TARGET | METHOD by defining the field mapping and giving a custom conversion function.

   // goverter:converter
   type ConverterWithMapCustom interface {
   // goverter:map Envs EnvKeys | ExtractKeys
   // goverter:map Envs EnvValues | ExtractValues
   Convert(Input) (Output, error)
   }

I'm not against an after hook, but I'd need a good example that's not fixable via default.

Full Example (click me)

```go // goverter:converter type ConverterWithMapCustom interface { // goverter:map Envs EnvKeys | ExtractKeys // goverter:map Envs EnvValues | ExtractValues Convert(Input) (Output, error) } // goverter:converter type ConverterWithDefault interface { // goverter:default PreProcess // goverter:ignore EnvKeys EnvValues Convert(Input) (Output, error) } func PreProcess(i Input) Output { return Output{EnvKeys: ExtractKeys(i.Envs), EnvValues: ExtractKeys(i.Envs)} } func ExtractKeys(envs []Env) []string { var result []string for _, env := range envs { result = append(result, env.Key) } return result } func ExtractValues(envs []Env) []string { var result []string for _, env := range envs { result = append(result, env.Value) } return result } type Input struct { Envs []Env Name string } type Env struct { Key string Value string } type Output struct { EnvKeys []string EnvValues []string Name string } ```

[hermanschaaf]

Ah got it, thanks! The trick I was missing was that you can actually map the same input field twice, as in:

// goverter:map Envs EnvKeys | ExtractKeys
// goverter:map Envs EnvValues | ExtractValues
Convert(Input) (Output, error)