Controller that displays a picker view as an input view to a text field on iPhone or in a popover on iPad.

RQSTextFieldOptionsController.h

//
//  RQSTextFieldOptionsController.h
//  Requests
//
//  Created by Daniel Tull on 03.10.2012.
//  Copyright (c) 2012 Daniel Tull. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface RQSTextFieldOptionsController : UIView
@property (nonatomic, weak) IBOutlet UITextField *textField;
@property (nonatomic, copy) NSArray *options;
@property (nonatomic, assign) UIPopoverArrowDirection popoverArrowDirection;
@end

RQSTextFieldOptionsController.m

//
//  RQSTextFieldOptionsController.m
//  Requests
//
//  Created by Daniel Tull on 03.10.2012.
//  Copyright (c) 2012 Daniel Tull. All rights reserved.
//

#import "RQSTextFieldOptionsController.h"
#import <objc/runtime.h>

void *RQSTextFieldOptionsControllerKey = &RQSTextFieldOptionsControllerKey;

@interface RQSTextFieldOptionsController () <UIPickerViewDataSource, UIPickerViewDelegate, UIPopoverControllerDelegate>
@property (nonatomic, strong) UIPickerView *pickerView;
@end

@implementation RQSTextFieldOptionsController {
	__strong UIPopoverController *_popoverController;
}

- (void)dealloc {
	[self.textField removeTarget:self action:@selector(textFieldEditingChanged:) forControlEvents:UIControlEventEditingChanged];
	
	UIUserInterfaceIdiom idiom = [[UIDevice currentDevice] userInterfaceIdiom];
	if (idiom == UIUserInterfaceIdiomPad) {
		[self.textField removeTarget:self action:@selector(textFieldEditingDidBegin:) forControlEvents:UIControlEventEditingDidBegin];
		[self.textField removeTarget:self action:@selector(textFieldEditingDidEndOnExit:) forControlEvents:UIControlEventEditingDidEnd];
	}
}

- (id)init {
	self = [super init];
	if (!self) return nil;
	_popoverArrowDirection = UIPopoverArrowDirectionAny;
	return self;
}

- (void)setTextField:(UITextField *)textField {
	
	objc_setAssociatedObject(_textField, RQSTextFieldOptionsControllerKey, nil, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
	_textField = textField;
	objc_setAssociatedObject(_textField, RQSTextFieldOptionsControllerKey, self, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
	
	[_textField addTarget:self action:@selector(textFieldEditingChanged:) forControlEvents:UIControlEventEditingChanged];
	[self _setDefaultOption];
	
	UIUserInterfaceIdiom idiom = [[UIDevice currentDevice] userInterfaceIdiom];
	
	if (idiom == UIUserInterfaceIdiomPad) {
		_textField.inputView = [UIView new];
		[_textField addTarget:self action:@selector(textFieldEditingDidBegin:) forControlEvents:UIControlEventEditingDidBegin];
		[_textField addTarget:self action:@selector(textFieldEditingDidEndOnExit:) forControlEvents:UIControlEventEditingDidEnd];
	} else if (idiom == UIUserInterfaceIdiomPhone)
		_textField.inputView = self.pickerView;
}

- (void)setOptions:(NSArray *)options {
	_options = [options copy];
	[self _setDefaultOption];
}

- (UIPickerView *)pickerView {
	
	if (!_pickerView) {
		_pickerView = [UIPickerView new];
		_pickerView.dataSource = self;
		_pickerView.delegate = self;
		_pickerView.showsSelectionIndicator = YES;
		[_pickerView selectRow:[self.options indexOfObject:self.textField.text] inComponent:0 animated:NO];
	}
	
	return _pickerView;
}

- (IBAction)textFieldEditingChanged:(id)sender {
	self.textField.text = [self pickerView:_pickerView titleForRow:[_pickerView selectedRowInComponent:0] forComponent:0];
	[self _sendTextFieldControlEvents];
}

- (IBAction)textFieldEditingDidEndOnExit:(id)sender {
	[_popoverController dismissPopoverAnimated:YES];
	_popoverController = nil;
}

- (IBAction)textFieldEditingDidBegin:(id)sender {
	UIPickerView *pickerView = self.pickerView;
	UIViewController *pickerViewController = [UIViewController new];
	pickerViewController.view.frame = pickerView.bounds;
	[pickerViewController.view addSubview:pickerView];

	_popoverController = [[UIPopoverController alloc] initWithContentViewController:pickerViewController];
	_popoverController.popoverContentSize = pickerView.bounds.size;
	_popoverController.delegate = self;
	_popoverController.passthroughViews = [self _allControlSubviews:[self _ancestorView:self.textField]];
	[_popoverController presentPopoverFromRect:self.textField.frame inView:self.textField.superview permittedArrowDirections:self.popoverArrowDirection animated:YES];
}

#pragma mark - Internal

- (UIView *)_ancestorView:(UIView *)view {
	while (view.superview)
		view = view.superview;
	return view;
}

- (NSArray *)_allControlSubviews:(UIView *)view {
	
	NSMutableArray *subviews = [NSMutableArray new];
	if ([view isKindOfClass:[UIControl class]] || [view isKindOfClass:[UITableViewCell class]])
		[subviews addObject:view];
	
	[view.subviews enumerateObjectsUsingBlock:^(UIView *v, NSUInteger idx, BOOL *stop) {
		[subviews addObjectsFromArray:[self _allControlSubviews:v]];
	}];
	
	return subviews;
}

- (void)_setDefaultOption {
	if ([self.options count] == 0) return;
	if ([self.textField.text length] > 0 && [self.options containsObject:self.textField.text]) return;
	self.textField.text = self.options[0];
	[self _sendTextFieldControlEvents];
}

- (void)_sendTextFieldControlEvents {
	[self.textField removeTarget:self action:@selector(textFieldEditingChanged:) forControlEvents:UIControlEventEditingChanged];
	[self.textField sendActionsForControlEvents:UIControlEventEditingChanged];
	[self.textField addTarget:self action:@selector(textFieldEditingChanged:) forControlEvents:UIControlEventEditingChanged];
}

#pragma mark - UIPopoverControllerDelegate

- (void)popoverControllerDidDismissPopover:(UIPopoverController *)popoverController {
	[self.textField resignFirstResponder];
}

#pragma mark - UIPickerViewDataSource

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
	return 1;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
	return [self.options count];
}

#pragma mark - UIPickerViewDelegate

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
	return self.options[row];
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
	self.textField.text = self.options[row];
	[self _sendTextFieldControlEvents];
}

@end