UITextView添加placeholder

//本文采用的代码量比较少的一种写法,测试中未出现bug
#import "ViewController.h"
#import "Masonry.h"

@interface ViewController ()
@property (nonatomic, strong) UITextView *textView;
@end
@implementation ViewController
- (void)viewDidLoad {
    [self.view addSubview:self.textView];
    [self.textView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view).offset(100);
        make.height.equalTo(@48);
        make.right.equalTo(self.inputView).offset(-20);
        make.left.equalTo(self.inputView).offset(20);
    }];

}
-(UITextView *)textView{
    if (!_textView) {
        _textView = [[UITextView alloc] init];
        _textView.font = [UIFont systemFontOfSize:14];
        _textView.textColor = MIN_BLACKTITLE_COLOR;
        UILabel *placeHolderLabel = [[UILabel alloc] init];
        placeHolderLabel.text = @"请输入您的评论";
        placeHolderLabel.textColor = [UIColor lightGrayColor];
        placeHolderLabel.font = [UIFont systemFontOfSize:14];
        [placeHolderLabel sizeToFit];
        [_textView addSubview:placeHolderLabel];
        [_textView setValue:placeHolderLabel forKey:@"_placeholderLabel"];
    }
    return _textView;
}
@end