how to use Echo#BindUnmarshaler to bind date time in v4

[shyandsy]

Issue Description

the frontend post expired time to server-side, like "2020-11-12 13:14:15"

the server-side try to bind this value to the expired field in the model class

u := &models.User{}
if err := c.Bind(u); err != nil {
	panic(err)
}

the error message shows below

{"message":"parsing time \"\"2020-11-12 13:11:12\"\" as \"\"2006-01-02T15:04:05Z07:00\"\": cannot parse \" 13:11:12\"\" as \"T\""}

I checked the document for Echo#BindUnmarshaler

https://echo.labstack.com/guide/request

unfortunately, the document only mentioned it, and no details for how to use it

Checklist

• Dependencies installed
• No typos
• Searched existing issues and docs

Expected behaviour

1. are there any way to change post data before bind to model, like below

c.FormValue("expired") = c.FormValue("expired") + "Z"

2. are there any way to bind the time with customize format， rather than time.RFC3339

Version/commit

V4

[matcornic]

Universal solution

One universal solution would be to use a custom UnmarshalJson on your time inside models.User type and basically parse the time with your format.

See Custom unmarshall JSON

I already did something like this with the XML unmarshaller (principle is the same):

type CustomTime time.Time

func (ct *CustomTime) String() string {
	return time.Time(*st).String()
}

func (ct *CustomTime) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	var s string
	err := d.DecodeElement(&s, &start)
	if err != nil {
		return err
	}
	t, err := time.Parse(`2006-01-02 15:04:05 MST`, s)
	if err != nil {
		return err
	}
	*st = CustomTime(t)
	return nil
}

Another solution (if possible) would be to use Moment.js on the front-end to send the right format to the server.

---

Echo solution

Echo solution is to implement the following interface:

	BindUnmarshaler interface {
		// UnmarshalParam decodes and assigns a value from an form or query param.
		UnmarshalParam(param string) error
	}

So you need to add a UnmarshalParam method to the custom time inside models.User type.

type CustomTime time.Time

func (ct *CustomTime) UnmarshalParam(param string) error {
        t, err := time.Parse(`2006-01-02 15:04:05 MST`, param)
	if err != nil {
		return err
	}
	*st = CustomTime(t)
	return nil
}

I did not test this solution though.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.