How to Restrict Emoji Input and Enforce Character Length in Swift (with UITextField & UITextView)

📘 Overview

When building iOS apps, you often want to:

• 🚫 Prevent users from typing emoji characters
• ✅ Allow only specific inputs like numbers, #, *
• 📏 Count string length accurately (UTF-8 or UTF-16)
• ⌨️ Enforce ASCII-capable keyboards only

In this blog, you’ll learn how to do all of that in a clean and reusable way using String extensions, UITextFieldDelegate, and UITextViewDelegate.

✅ Goals

• ❌ Disallow emojis in UITextField and UITextView
• ✅ Allow special characters like 0-9, #, *
• 🧠 Detect input length by utf8.count or utf16.count
• ⌨️ Force ASCII-capable keyboard

💡 1. Create String Extension

import Foundation

extension String {
    
    var utf8Length: Int {
        return self.utf8.count
    }

    var utf16Length: Int {
        return self.utf16.count
    }

    var hasEmoji: Bool {
        return self.unicodeScalars.contains { scalar in
            switch scalar.value {
            case 0x30...0x39,        // '0' to '9' should not be considered emoji i.e. number
                 0x0023,             // '#'
                 0x002A:             // '*'
                 return false
            case 0x1F600...0x1F64F,  // Emoticons (e.g., 😀😃😄😁😆)
                0x1F300...0x1F5FF,   // Misc Symbols and Pictographs (e.g., 🌸🎉💡🚿📚)
                0x1F680...0x1F6FF,   // Transport and Map Symbols (e.g., 🚗✈️🚀🚉⛵️)
                0x1F1E6...0x1F1FF,   // Regional Indicator Symbols (used for country flags 🇮🇳🇺🇸)
                0x2600...0x26FF,     // Misc Symbols (e.g., ☀️☁️☂️☹️♻️♠️)
                0x2700...0x27BF,     // Dingbats (e.g., ✂️✈️✉️⚠️☑️)
                0x1F900...0x1F9FF,   // Supplemental Symbols and Pictographs (e.g., 🤖🦄🥑🧠🦷)
                0x1F018...0x1F270,   // Various emoji-like symbols (e.g., 🀄️🃏🔞🕐)
                0x238C...0x2454,     // Misc technical symbols (e.g., ⏰⏳⏭️⏮️⏸️)
                0x20D0...0x20FF:     // Combining Diacritical Marks for Symbols (variation selectors like ⃠️)
                return true
            default:
                return scalar.properties.isEmoji  // Fallback check for any other emoji
            }
        }
    }
}

💡 2. Enforce Emoji Restriction in UITextField & UITextView

extension ViewController: UITextViewDelegate, UITextFieldDelegate {
    
    func textView(_ textView: UITextView,
                  shouldChangeTextIn range: NSRange,
                  replacementText text: String) -> Bool {
        return !text.hasEmoji
    }

    func textField(_ textField: UITextField,
                   shouldChangeCharactersIn range: NSRange,
                   replacementString string: String) -> Bool {
        
        // Restrict emojis in specific text field
        if textField == specificTextField {
            return !string.hasEmoji
        }
        
        return true
    }
}

💡 3. Force ASCII Keyboard Type

override func viewDidLoad() {
    super.viewDidLoad()

    specificTextField.delegate = self
    abcTextView.delegate = self
    
    specificTextField.keyboardType = .asciiCapable
    abcTextView.keyboardType = .asciiCapable
}

💡 4. Dismiss Keyboard on Tap Outside (Optional UX Tip)

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    self.view.endEditing(true)
}

🧪 Test It Out

debugPrint("Hello".hasEmoji)         // false
debugPrint("123".hasEmoji)           // false
debugPrint("speical ✈️".hasEmoji)    // true
debugPrint("Hello 😃".hasEmoji)      // true

✨ Bonus: Length Validation Example

if inviteNameTextField.text?.utf16Length ?? 0 > 160 {
    print("Text exceeds UTF-16 byte limit")
}

🔚 Conclusion

With a few lines of reusable code:

• You protect your inputs from emojis
• Maintain database-safe character limits
• Ensure cleaner UX and backend consistency

This is ideal for forms, signups, chat inputs, payment fields, or any strict validation flow in your app.

🔖 Summary Checklist

✅ Emoji check in String extension
✅ Limit text input using UITextFieldDelegate & UITextViewDelegate
✅ Enforce .asciiCapable keyboard
✅ Optional: Limit text length using .utf16Length

Appreciate you going through this — if it helped in any way, feel free to like or share!