Separate param binding from param validation

[bblack]

Feature Description

In my gin application, we have endpoints that depend on parameters located in more than one place: e.g. in the uri (POST /org/:id/user) and the body, assumed to be json. I'd like to bind those to a single go struct, like

type GetUsersParams {
  orgId int
  name string
  role string
}

I want to be able to populate this single params struct with a single function call, looking for params in both URI and body (as json), regardless of whether each param is found in one place or the other, and assuming json regardless of whether the client passed content-type.

Unfortunately, we can't simply call shouldBindURI then shouldBindJSON, because each of those will return an error if ANY of the required GetUsersParams are absent from that particular location.

If I could call versions of these functions simply didn't call validate as their last step, and then called validate myself once at the end, this would be simple.

[Nurysso]

Hey I think you can do this by binding URL and JSON separately then combining them.

Something like this

func CreateUser(c *gin.Context) {
    // Bind URI params
    var uriParams struct {
        OrgID int `uri:"id" binding:"required"`
    }
    if err := c.ShouldBindUri(&uriParams); err != nil {
        c.JSON(400, gin.H{"error": err.Error()})
        return
    }
    // Bind JSON body
    var bodyParams struct {
        Name string `json:"name" binding:"required"`
        Role string `json:"role" binding:"required"`
    }
    if err := c.ShouldBindJSON(&bodyParams); err != nil {
        c.JSON(400, gin.H{"error": err.Error()})
        return
    }
    
    // Combine into your final struct
    params := GetUsersParams{
        OrgID: uriParams.OrgID,
        Name:  bodyParams.Name,
        Role:  bodyParams.Role,
    }
    
    // Use params...
}

This way each binding validates only its own fields, and you get all params in a single struct at the end.