自定义可设置placeholder的UITextView

iOS自带的UITextView无法像UITextField一样设置placeholder属性，而现实中这种设置又比较常用，第一次写这玩意，有错误麻烦大家给指出，有更简便的实现望大家不吝赐教。本人菜鸟一枚。

#import <UIKit/UIKit.h>

/**
 自定义带有plcaceholder的UITextView
 */
@interface RSPlaceholderTextView : UITextView

@property(nonatomic,copy)   NSString*   placeholder;
@property(nonatomic,strong) UIColor*    placeholderColor;
@end

#import "RSPlaceholderTextView.h"

@interface RSPlaceholderTextView()<UITextViewDelegate>{
    BOOL                                        _showPlaceholder;
}

/**
 保存外部代理
 */
@property(nonatomic,weak) id<UITextViewDelegate>            rsDelegate;
@end

@implementation RSPlaceholderTextView

- (instancetype)initWithFrame:(CGRect)frame{
    self = [super initWithFrame:frame];
    if (self) {
        _showPlaceholder = YES;
        super.delegate = self;
        _placeholderColor = [UIColor colorWithRed:199/255.0 green:199/255.0 blue:205/255.0 alpha:1];
    }
    return self;
}

- (void)drawRect:(CGRect)rect{
    if (_showPlaceholder && _placeholder) {
        NSMutableDictionary* attibute = [NSMutableDictionary dictionary];
        [attibute setObject:_placeholderColor forKey:NSForegroundColorAttributeName];
        if (self.font) {
            [attibute setObject:self.font forKey:NSFontAttributeName];
        }
        [_placeholder drawAtPoint:CGPointMake(self.textContainerInset.left+5, self.textContainerInset.top) withAttributes:attibute];
    }
}
#pragma mark - setter
- (void)setPlaceholder:(NSString *)placeholder{
    _placeholder = placeholder.copy;
    [self setNeedsDisplay];
}

- (void)setPlaceholderColor:(UIColor *)placeholderColor{
    _placeholderColor = placeholderColor;
    [self setNeedsDisplay];
}

- (void)setFont:(UIFont *)font{
    [super setFont:font];
    [self setNeedsDisplay];
}

- (void)setDelegate:(id<UITextViewDelegate>)delegate{
    _rsDelegate = delegate;
}

- (void)setText:(NSString *)text{
    [super setText:text];
    if ((text.length > 0 && _showPlaceholder) || (text.length == 0 &&       
        !_showPlaceholder)) {
        _showPlaceholder = !_showPlaceholder;
        [self setNeedsDisplay];
    }
}

#pragma mark - UITextViewDelegate
- (BOOL)textViewShouldBeginEditing:(UITextView *)textView{
    if ([_rsDelegate respondsToSelector:@selector(textViewShouldBeginEditing:)]) {
        return [_rsDelegate textViewShouldBeginEditing:textView];
    }
    return YES;
}

- (BOOL)textViewShouldEndEditing:(UITextView *)textView{
    if ([_rsDelegate respondsToSelector:@selector(textViewShouldEndEditing:)]) {
        return [_rsDelegate textViewShouldEndEditing:textView];
    }
    return YES;
}

- (void)textViewDidBeginEditing:(UITextView *)textView{
    if ([_rsDelegate respondsToSelector:@selector(textViewDidBeginEditing:)]) {
        [_rsDelegate textViewDidBeginEditing:textView];
    }
}

- (void)textViewDidEndEditing:(UITextView *)textView{
    if ([_rsDelegate respondsToSelector:@selector(textViewDidEndEditing:)]) {
        [_rsDelegate textViewDidEndEditing:textView];
    }
}

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{
    if ([_rsDelegate respondsToSelector:@selector(textView:shouldChangeTextInRange:replacementText:)]) {
        return [_rsDelegate textView:textView shouldChangeTextInRange:range replacementText:text];
    }
    return YES;
}

- (void)textViewDidChange:(UITextView *)textView{
   if (textView.text.length > 0 && _showPlaceholder) {
        _showPlaceholder = NO;
        [self setNeedsDisplay];
    }else if(textView.text.length == 0 && !_showPlaceholder){
        _showPlaceholder = YES;
        [self setNeedsDisplay];
    }
    if ([_rsDelegate respondsToSelector:@selector(textViewDidChange:)]) {
        [_rsDelegate textViewDidChange:textView];
    }
}

- (void)textViewDidChangeSelection:(UITextView *)textView{
    if ([_rsDelegate respondsToSelector:@selector(textViewDidChangeSelection:)]) {
        [_rsDelegate textViewDidChangeSelection:textView];
    }
}

- (BOOL)textView:(UITextView *)textView shouldInteractWithURL:(NSURL *)URL inRange:(NSRange)characterRange interaction:(UITextItemInteraction)interaction NS_AVAILABLE_IOS(10_0){
    if ([_rsDelegate respondsToSelector:@selector(textView:shouldInteractWithURL:inRange:interaction:)]) {
        return [_rsDelegate textView:textView shouldInteractWithURL:URL inRange:characterRange interaction:interaction];
    }
    return YES;
}
- (BOOL)textView:(UITextView *)textView shouldInteractWithTextAttachment:(NSTextAttachment *)textAttachment inRange:(NSRange)characterRange interaction:(UITextItemInteraction)interaction NS_AVAILABLE_IOS(10_0){
    if ([_rsDelegate respondsToSelector:@selector(textView:shouldInteractWithTextAttachment:inRange:interaction:)]) {
        return [_rsDelegate textView:textView shouldInteractWithTextAttachment:textAttachment inRange:characterRange interaction:interaction];
    }
    return YES;
}
@end

使用方法和UITextField一样

RSPlaceholderTextView* textView = [[RSPlaceholderTextView alloc] initWithFrame:CGRectMake(10, 20, CGRectGetWidth(self.view.frame)-20, 100)];
textView.font = [UIFont systemFontOfSize:20];
textView.placeholder = @"测试一下";
textView.delegate = self;
[self.view addSubview:textView];