【Swift】検索フォームを実装する方法を実用的なサンプルコードを示しつつ詳細に解説！

import UIKit

class SearchViewController: UIViewController, UITextFieldDelegate {

    let searchTextField: UITextField = {
        let textField = UITextField()
        textField.placeholder = "検索..."
        textField.borderStyle = .roundedRect
        return textField
    }()

    let searchButton: UIButton = {
        let button = UIButton(type: .system)
        button.setTitle("検索", for: .normal)
        return button
    }()
    
    let resultLabel: UILabel = {
        let label = UILabel()
        label.numberOfLines = 0 // 複数行を許可
        label.textAlignment = .center
        label.text = "検索結果はこちらに表示されます"
        return label
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        setupSearchTextField()
        setupSearchButton()
        setupResultLabel()
    }

    func setupSearchTextField() {
        view.addSubview(searchTextField)
        searchTextField.translatesAutoresizingMaskIntoConstraints = false
        searchTextField.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 20).isActive = true
        searchTextField.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20).isActive = true
        searchTextField.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20).isActive = true
        searchTextField.delegate = self
    }

    func setupSearchButton() {
        view.addSubview(searchButton)
        searchButton.translatesAutoresizingMaskIntoConstraints = false
        searchButton.topAnchor.constraint(equalTo: searchTextField.bottomAnchor, constant: 20).isActive = true
        searchButton.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        searchButton.addTarget(self, action: #selector(searchButtonTapped), for: .touchUpInside)
    }
    
    func setupResultLabel() {
        view.addSubview(resultLabel)
        resultLabel.translatesAutoresizingMaskIntoConstraints = false
        resultLabel.topAnchor.constraint(equalTo: searchButton.bottomAnchor, constant: 20).isActive = true
        resultLabel.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20).isActive = true
        resultLabel.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20).isActive = true
    }

    @objc func searchButtonTapped() {
        // 検索処理をここに記述
        guard let searchText = searchTextField.text, !searchText.isEmpty else { return }
        performSearch(with: searchText)
    }

    func performSearch(with keyword: String) {
        // 仮想的な検索結果を生成
        let searchResults = ["結果1", "結果2", "結果3"].filter { $0.contains(keyword) }
        updateSearchResults(searchResults)
    }
    
    func updateSearchResults(_ results: [String]) {
        // 検索結果が空の場合は「結果なし」と表示
        if results.isEmpty {
            resultLabel.text = "結果なし"
        } else {
            // 検索結果をラベルに表示
            resultLabel.text = results.joined(separator: "\n")
        }
    }
}