1、解决问题

众所周知UITextField有一个 placeholder属性，起到占位文字或者是提示的作用，但是UITextView却没有这样一个属性，本文就是为了解决这个问题

2、封装一个RWTextView

RWTextView.h

#import <UIKit/UIKit.h>

@interface RWTextView : UIView

/**
 * 创建一个带有占位文字的UITextView的对象View
 */
+ (instancetype)textView;

/**
 *  占位文字
 */
@property (nonatomic, copy) NSString *placeholder;
/**
 *  占位文字的字体大小
 */
@property (nonatomic, assign) CGFloat placeholderFout;
/**
 *  占位文字的字体颜色
 */
@property (nonatomic, strong) UIColor *placeholderTitleColor;

@end

RWTextView.m

#import "RWTextView.h"

@interface RWTextView ()<UITextViewDelegate>

/**
 *  占位文字
 */
@property (nonatomic, strong) UILabel *placeHolderLabel;

/**
 *  UITextView
 */
@property (nonatomic, strong) UITextView *textView;

@end

@implementation RWTextView

/**
 * 创建一个带有占位文字的UITextView的对象View 类方法的实现
 */
+ (instancetype)textView {
    
    return [[self alloc] init];
}

/**
 * 初始化子控件
 */
- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        
        /** 1、创建 占位文字 */
        UILabel *placeHolderLabel = [[UILabel alloc] init];
        self.placeHolderLabel = placeHolderLabel;
        self.placeHolderLabel.textColor = [UIColor lightGrayColor];
        [self addSubview:placeHolderLabel];
        
        /** 2、创建 UItextView */
        UITextView *textView = [[UITextView alloc] init];
        textView.delegate = self;
        textView.backgroundColor = [UIColor clearColor];
        textView.backgroundColor = [UIColor brownColor];
        textView.alpha = 0.3;
        textView.tintColor = [UIColor yellowColor];
        self.textView = textView;
        [self addSubview:textView];
    }
    return self;
}

/** 子控件布局 */
- (void)layoutSubviews {
    
    [super layoutSubviews];
    self.placeHolderLabel.frame = CGRectMake(5, 0, self.bounds.size.width, 30);
    self.textView.frame = self.bounds;
}

/** 设置占位文字 */
- (void)setPlaceholder:(NSString *)placeholder {

    _placeholder = placeholder;
    
    self.placeHolderLabel.text = self.placeholder;
  
}

/** 设置占位文字字体大小 */
- (void)setPlaceholderFout:(CGFloat)placeholderFout {

    _placeholderFout = placeholderFout;
    self.placeHolderLabel.font = [UIFont systemFontOfSize:placeholderFout];
}

/** 设置占位文字颜色 */
- (void)setPlaceholderTitleColor:(UIColor *)placeholderTitleColor {

    _placeholderTitleColor = placeholderTitleColor;
    
    self.placeHolderLabel.textColor = placeholderTitleColor;
}

#pragma mark - UITextViewDelegate代理
#pragma mark - 监听textView中内容的改变
- (void)textViewDidChange:(UITextView *)textView {
    
    if (!textView.text.length) {
        //显示提示文字
        self.placeHolderLabel.hidden = NO;
    } else {
        //隐藏提示文字
        self.placeHolderLabel.hidden = YES;
    }
}

3、完整调用封装 对象

#import "ViewController.h"
#import "RWTextView.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    //1、创建textView
    RWTextView *textView = [RWTextView textView];
    textView.placeholder = @"textView中的placeholder";
    textView.frame = CGRectMake(100, 100, 200, 100);
    textView.placeholderTitleColor = [UIColor lightGrayColor];
    textView.placeholderFout = 14;
    textView.backgroundColor = [UIColor whiteColor];
    [self.view addSubview:textView];
}

@end