TextView with a Placeholder option

TTPlaceholderTextView.h

//
//  TTPlaceholderTextView.h
//
//  Created by Joshua Johnson on 1/6/12.
//  Copyright (c) 2012 Two Toasters. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface TTPlaceholderTextView : UITextView

@property (nonatomic, retain) UIColor *placeholderColor;
@property (nonatomic, copy) NSString *placeholderText;

@end

TTPlaceholderTextView.m

//
//  TTPlaceholderTextView.m
//
//  Created by Joshua Johnson on 1/6/12.
//  Copyright (c) 2012 Two Toasters. All rights reserved.
//

#import "TTPlaceholderTextView.h"

@interface TTPlaceholderTextView ()

@property (nonatomic, assign) BOOL shouldDrawPlaceholder;

- (void)contentDidChange:(NSNotification *)notification;
- (CGRect)proportionalInsetRectFromRect:(CGRect)rect inset:(CGFloat)inset;

@end


@implementation TTPlaceholderTextView

#pragma mark - synth

@synthesize placeholderText = _placeholderText, _placeholderColor = _placeholderColor;
@synthesize shouldDrawPlaceholder = _shouldDrawPlaceholder;

#pragma mark - lifecycle

- (id)initWithFrame:(CGRect)frame 
{
    if (self = [super initWithFrame:frame]) {
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(contentDidChange:) name:UITextViewTextDidChangeNotification object:self];
        
        _placeholderColor = [[UIColor lightGrayColor] retain];
        _shouldDrawPlaceholder = YES;
        [self setNeedsDisplay];
    }
    return self;
}

- (void)dealloc 
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    [_placeholderText release];
    [_placeholderColor release];
    [super dealloc];
}

#pragma mark - Drawing

- (void)drawRect:(CGRect)rect 
{
    [super drawRect:rect];
    
    if (_shouldDrawPlaceholder) {
        [_placeholderColor set];
        [_placeholderText drawInRect:[self proportionalInsetRectFromRect:rect inset:8.0] withFont:[self font]];
    }
}

#pragma mark - helpers

- (CGRect)proportionalInsetRectFromRect:(CGRect)rect inset:(CGFloat)inset
{
    CGFloat insets = inset * 2;
    return (CGRect){rect.origin.x + inset, rect.origin.y + inset, rect.size.width - insets, rect.size.height - insets};
}

#pragma mark - notification

- (void)contentDidChange:(NSNotification *)notification
{
    BOOL previousState = _shouldDrawPlaceholder;
    _shouldDrawPlaceholder = _placeholderText && _placeholderColor && [[self text] length] == 0;
    if (previousState != _shouldDrawPlaceholder) {
        [self setNeedsDisplay];
    }
}

@end