UITextView添加placeholder属性

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给UITextView添加placeholder属性网上也有很多，我在这里提供最简洁的方法给已解决。主要方法是给UITextView添加分类，再利用KVC对UITextView的私有属性“_placeholderLabel”修改。直接上代码了。

#import <UIKit/UIKit.h>@interface UITextView (Placeholder)-(void)setPlaceholder:(NSString *)placeholdStr placeholdColor:(UIColor *)placeholdColor;@end#import "UITextView+Placeholder.h"@implementation UITextView (Placeholder)-(void)setPlaceholder:(NSString *)placeholdStr placeholdColor:(UIColor *)placeholdColor{    UILabel *placeHolderLabel = [[UILabel alloc] init];    placeHolderLabel.text = placeholdStr;    placeHolderLabel.numberOfLines = 0;    placeHolderLabel.textColor = placeholdColor;    placeHolderLabel.font = self.font;    [placeHolderLabel sizeToFit];    [self addSubview:placeHolderLabel];    /*     [self setValue:(nullable id) forKey:(nonnull NSString *)]     ps: KVC键值编码，对UITextView的私有属性进行修改     */    [self setValue:placeHolderLabel forKey:@"_placeholderLabel"];}@end    //方法的实现部分（记得导入头文件"UITextView+Placeholder.h"）    UITextView *contentTextView = [[UITextView alloc] initWithFrame:CGRectMake(10, 300, 300, 60)];    contentTextView.layer.cornerRadius = 6;    contentTextView.layer.borderWidth = 0.6;    contentTextView.layer.borderColor = [UIColor grayColor].CGColor;    contentTextView.layer.masksToBounds = YES;    contentTextView.font = [UIFont systemFontOfSize:13];    //调用私有方法    [contentTextView setPlaceholder:@"这是placeholder文字..." placeholdColor:[UIColor lightGrayColor]];    [self.view addSubview:contentTextView];

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