如果为空，则将值分配给struct中的字段

Question

I have a struct defined

type data struct {
  invitecode string
  fname string
  lname string
}

which I populate from retrieving form data after parsing

...

r.ParseForm()

new user := &data{
  invitecode: r.FormValue("invitecode"),
  fname: r.FormValue("fname")
  lname: r.FormValue("lname")
}

I did like to check if the invitecode field obtained from the form is empty and if so, populate it by calling a function but if it is not, to populate it with the retrieved value (invitecode: if newUser.invitecode == "" {"Mr"} else {lnames.title},). I understand go doesn't have a tenary operator which I thought of using and reading the questions here, here, here & here implies using an if else statement but I can't seem to get it to work. Preferable, I am looking for a solution that check's while assigning a new variable. Trying the code below doesn't seem to work. Any help would be appreciated.

package main

import (
    "fmt"
)

type data struct {
    invitecode string
    fname      string
    lname      string
}

func main() {
    var user data

    newUser := map[string]string{"invitecode": "", "fname": "Dude", "lname": "Did"}
    user = &data{
        invitecode: if newUser.invitecode == "" {"Mr"} else {lnames.title},
        fname:      newUser.fname,
        lname:      newUser.lname,
    }
    fmt.Println(user)
}

Answer 1

Go does not have ternaries, nor can you do an inline if like you've shown in the code. You will have to do a normal if block:

user = &data{}
if newUser.inviteCode = "" {
    user.invitecode = "Mr"
} else {
    user.invitecode = lnames.title
}

And so on. You could extract this into a function:

func coalesce(args ...string) string {
    for _,str := range args {
        if str != "" {
            return str
        }
    }
    return ""
}

And use it like so:

user.invitecode = coalesce(lnames.title, "Mr")

Of course, if you deal with multiple types (not just strings), you'll need one such function for each type.