How to add a method to UITextField & UITextView? - iphone

Question

I want to put something like this in a method for UITextField & UITextView.
- (void)changeKeyboardType:(UIKeyboardType)keyboardType {
paymentTextView.keyboardType = UIKeyboardTypeAlphabet;
[paymentTextView resignFirstResponder];
[paymentTextView becomeFirstResponder];
}
How do I do this? I know I can create categories for both UITextField & UITextView but is it possible to do it in one shot?
By one shot, I mean add it to both classes with one protocol instead of making two categories, one for UITextView & one for UITextField. I've heard a protocol is similar to a Ruby module, but in a Ruby module, I can implement the method. In a protocol, it only seems that I can declare the method but not implement it. Can I also implement the method in the protocol, and then include this protocol in UITextField & UITextView?
How to add a method to an existing protocol in Cocoa? is close but not quite.

Answer 1

What about something like this?
// UIView+UITextInputTraits.h
#interface UIView (UITextInputTraits)
- (void)changeKeyboardType:(UIKeyboardType)keyboardType;
#end
// UIView+Additions.m
#import "UIView+UITextInputTraits.h"
#implementation UIView (UITextInputTraits)
- (void)changeKeyboardType:(UIKeyboardType)keyboardType {
if ([self conformsToProtocol:#protocol(UITextInputTraits)]) {
id<UITextInputTraits> textInput = (id<UITextInputTraits>)self;
if (textInput.keyboardType != keyboardType) {
[self resignFirstResponder];
textInput.keyboardType = keyboardType;
[self becomeFirstResponder];
}
}
}
#end

Answer 2

For each of these, you can create a category.
Interface file:
#interface UITextField (ChangeKeyboard)
- (void)changeKeyboardType:(UIKeyboardType)keyboardType;
#end
Implementation file:
#implementation UITextField (ChangeKeyboard)
- (void)changeKeyboardType:(UIKeyboardType)keyboardType {
self.keyboardType = keyboardType;
[self resignFirstResponder];
[self becomeFirstResponder];
}
#end
That would be the way to add these, but I haven't tested the functionality.

Answer 3

Like #Josh said, method swizzling isn't what you are looking for. However what I actually had in mind (My bad for not researching more into it before submitting an answer) is to add method at runtime on UITextView and UITextField. While this needs a bit more code to implement, it can give you the sort of one-shot you are looking for (You create a method and add it to both UITextView & UITextField at run-time)
Here's a blog post about it:
http://theocacao.com/document.page/327
http://www.mikeash.com/pyblog/friday-qa-2010-11-6-creating-classes-at-runtime-in-objective-c.html