@IBActionのメソッドでエラーが出た時の対処法について

前提・実現したいこと

日記のアプリを作り終わったときに前から書いていた@IBActionのメソッドにエラーが出ました。
別のファイルで@IBActionを書いているのですが、そちらには何もエラーは出なく、どこが違うのかもさっぱりです...

発生している問題・エラーメッセージ

Only instance methods can be declared @IBAction

該当のソースコード

swift
1  @IBAction func saveButtonPushed(_ sender: UIButton) {
2
3            let realm = try! Realm()
4
5            let diary = Diary()
6            diary.date = date
7            diary.context = contextTextView.text
8
9            try! realm.write {
10                realm.add(diary, update: true)
11            }
12            self.dismiss(animated: true, completion: nil) 
13        }

DiaryViewController

import UIKit
import RealmSwift

class DiaryViewController: UIViewController {
    
    @IBOutlet var dateLabel: UILabel!
    @IBOutlet var saveButton: UIButton!
    @IBOutlet var contextTextView: UITextView!
    
    var date: String! 
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        dateLabel.text = date
        
        DispatchQueue(label: "background").async {

            let realm = try! Realm()
            
            if let savedDiary = realm.objects(Diary.self).filter("date == '(self.date!)'").last {

                let context = savedDiary.context
                DispatchQueue.main.async {
                    self.contextTextView.text = context
                }
            }
        }

            @IBAction func saveButtonPushed(_ sender: UIButton) {

            let realm = try! Realm()

            let diary = Diary()
            diary.date = date
            diary.context = contextTextView.text

            try! realm.write {
                realm.add(diary, update: true)
            }

            self.dismiss(animated: true, completion: nil)
            
        }
    }
}

Diary

import Foundation
import RealmSwift

class Diary: Object {
    @objc dynamic var date = ""
    @objc dynamic var context = ""
    @objc dynamic var photo: NSData? = nil
    
    override static func primaryKey() -> String? {
        return "date"
    }
    
}