Missing required parameter when just trying to pass "user" in - swiftui

Question

Trying to figure out why its requiring a parameter now when I was just trying to pass in a variable. Had generic text as placeholders for "user.username" and "user.fullname" and when "let user: User" is removed it runs as intended. When added however, the RowView in the previews requires a "user:" parameter.
import SwiftUI
struct RowView: View {
let user: User
var body: some View {
HStack(spacing: 12) {
Circle()
.frame(width: 48, height: 48)
VStack(alignment: .leading, spacing: 4) {
Text(user.username)
.font(.subheadline).bold()
.foregroundColor(.black)
Text(user.fullname)
.font(.subheadline)
.foregroundColor(.gray)
}
Spacer()
}
.padding(.horizontal)
.padding(.vertical)
}
}
struct RowView_Previews: PreviewProvider{
static var previews: some View {
RowView()
}
}

Answer 1

Declaring user without a starting value indicates that user is a required parameter for the view to be initialized. In the RowView_Previews, which is the preview for the view in the canvas, the RowView is being initialized without the user value. So you essentially have 3 options to fix this:
1. Pass in a user object for the preview
This is probably the best solution. You can pass in a new user object for the preview content:
static var previews: some View {
RowView(user: User())
}
2. Give user a default value
You could give user a default value, meaning that it is no longer a requirement to pass in a user object to initialize RowView:
let user: User = User()
3. Remove the preview provider altogether
If you don't use the previews (which I highly recommend you should), then you could just remove this part altogether, as it is not a requirement for the app to compile:
struct RowView_Previews: PreviewProvider{
static var previews: some View {
RowView()
}
}

Answer 2

you have a variable let user: User so you need to provide the value from anywhere you want to call this class.
See your preview is showing an error. click the error and click fix . then provide User().
or add this code :
struct RowView_Previews: PreviewProvider{
static var previews: some View {
RowView(user: User())
}
}
Or give a default value when you declare the variable . then no need to provide from preview .
like this code:
import SwiftUI
struct RowView: View {
let user: User = User()
var body: some View {
}
}

Answer 3

A usual way to provide default data for the preview is to add a static property to the User struct for example
struct User {
let username, fullname: String
static let example = User(username: "John", fullname: "John Doe")
}
and use it
struct RowView_Previews: PreviewProvider{
static var previews: some View {
RowView(user: User.example)
}
}
By the way
.padding(.horizontal)
.padding(.vertical)
does the same as
.padding()
And it's highly recommended to replace the colors .black with .primary (which is the default) and .gray with .secondary to have an adapted appearance in dark mode.