TextViewについて

ContentView.swift

//
//  ContentView.swift
//  TextFieldPractice
//
//  Created by Katsuyoshi Ito on 2023/01/10.
//

import SwiftUI

// CoreDataを想定してOptionalを扱うモデルを用意
struct Person {
    var name: String? = nil
}

struct ContentView: View {
    @State var person = Person()
    @State var name: String = ""
    @FocusState var isFocused: Bool
    let invalidColor = Color(red: 1.0, green: 0.7, blue: 0.7)
    var body: some View {
        VStack {
            TextField("Name", text: $name) { editing in
                if editing == false {
                    if isValid {
                        person.name = name
                    } else {
                        isFocused = true
                    }
                }
            }
            .focused($isFocused)
            .background(RoundedRectangle(cornerRadius: 2).fill(isValid ? .clear : invalidColor))
        }
        .padding()
        .onAppear() {
            // Optionalの値は一旦nameに展開
            name = person.name ?? ""
        }
    }
    
    private var isValid: Bool {
        return !name.isEmpty
    }
}

struct ContentView_Previews:
    PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}