UITextView with placeholder

Стандартный компонент UITextView не имеет placeholder, поэтому следует разработать подкласс этого компонента, который бы имел placeholder.

UIPlaceHolderTextView.h

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
 
 
@interface UIPlaceHolderTextView : UITextView {
    NSString *placeholder;
    UIColor *placeholderColor;
 
@private
    UILabel *placeHolderLabel;
}
 
@property (nonatomic, retain) UILabel *placeHolderLabel;
@property (nonatomic, retain) NSString *placeholder;
@property (nonatomic, retain) UIColor *placeholderColor;
 
-(void)textChanged:(NSNotification*)notification;
 
@end

UIPlaceHolderTextView.m

#import "UIPlaceHolderTextView.h"
 
 
@implementation UIPlaceHolderTextView
 
@synthesize placeHolderLabel;
@synthesize placeholder;
@synthesize placeholderColor;
 
- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
#if __has_feature(objc_arc)
#else
    [placeHolderLabel release]; placeHolderLabel = nil;
    [placeholderColor release]; placeholderColor = nil;
    [placeholder release]; placeholder = nil;
    [super dealloc];
#endif
 
}
 
- (void)awakeFromNib
{
    [super awakeFromNib];
    [self setPlaceholder:@""];
    [self setPlaceholderColor:[UIColor lightGrayColor]];
    [[NSNotificationCenter defaultCenter] addObserver:self 
      selector:@selector(textChanged:) 
      name:UITextViewTextDidChangeNotification object:nil];
}
 
- (id)initWithFrame:(CGRect)frame
{
    if( (self = [super initWithFrame:frame]) )
    {
        [self setPlaceholder:@""];
        [self setPlaceholderColor:[UIColor lightGrayColor]];
        [[NSNotificationCenter defaultCenter] addObserver:self 
          selector:@selector(textChanged:) 
          name:UITextViewTextDidChangeNotification object:nil];
    }
    return self;
}
 
- (void)textChanged:(NSNotification *)notification
{
    if([[self placeholder] length] == 0)
    {
        return;
    }
 
    if([[self text] length] == 0)
    {
        [[self viewWithTag:999] setAlpha:1];
    }
    else
    {
        [[self viewWithTag:999] setAlpha:0];
    }
}
 
- (void)setText:(NSString *)text {
    [super setText:text];
    [self textChanged:nil];
}
 
- (void)drawRect:(CGRect)rect
{
    if( [[self placeholder] length] > 0 )
    {
        if ( placeHolderLabel == nil )
        {
            placeHolderLabel = [[UILabel alloc] 
              initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];
            placeHolderLabel.lineBreakMode = NSLineBreakByWordWrapping;
            placeHolderLabel.numberOfLines = 0;
            placeHolderLabel.font = self.font;
            placeHolderLabel.backgroundColor = [UIColor clearColor];
            placeHolderLabel.textColor = self.placeholderColor;
            placeHolderLabel.alpha = 0;
            placeHolderLabel.tag = 999;
            [self addSubview:placeHolderLabel];
        }
 
        placeHolderLabel.text = self.placeholder;
        [placeHolderLabel sizeToFit];
        [self sendSubviewToBack:placeHolderLabel];
    }
 
    if( [[self text] length] == 0 && [[self placeholder] length] > 0 )
    {
        [[self viewWithTag:999] setAlpha:1];
    }
 
    [super drawRect:rect];
}
 
@end