iOS UITextView的PlaceHolder 占位文字的实现

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UITextView的PlaceHolder 占位文字的实现方法网上已经有很多了，特别是 VV木公 的 史上最全的iOS之UITextView实现placeHolder占位文字的N种方法 文章里面总结的很全面，我只是对里面最后一种方法封装了一下，方便以后偷懒 ~ 嘻嘻

个人感觉偷懒没有比类别更好的了

.h 文件

#import <UIKit/UIKit.h>

@interface UITextView (PlaceHolder)

/** 占位文字 */
@property (copy, nonatomic) NSString *placeHoldString;

/** 占位文字颜色 */
@property (strong, nonatomic) UIColor *placeHoldColor;

/** 占位文字字体 */
@property (strong, nonatomic) UIFont *placeHoldFont;



@end

.m文件

#import "UITextView+PlaceHolder.h"
#import <objc/runtime.h>

static NSString *placeHoldLabelKey = @"placeHoldLabelKey";
static NSString *placeHoldStringKey = @"placeHoldStringKey";
static NSString *placeHoldColorKey = @"placeHoldColorKey";
static NSString *placeHoldFontKey = @"placeHoldFontKey";

@interface UITextView()

@property (strong, nonatomic) UILabel *placeLabel;

@end


@implementation UITextView (PlaceHolder)

- (void)setPlaceLabel:(UILabel *)placeLabel{
    objc_setAssociatedObject(self, &placeHoldLabelKey, placeLabel, OBJC_ASSOCIATION_RETAIN);
}

- (UILabel *)placeLabel{
    return objc_getAssociatedObject(self, &placeHoldLabelKey);
}



- (void)setPlaceHoldString:(NSString *)placeHoldString{
    
    if (!self.placeLabel) {
        
        self.placeLabel = [self setupCustomPlaceHoldLabel];
    }
    
    self.placeLabel.text = placeHoldString;
    objc_setAssociatedObject(self, &placeHoldStringKey, placeHoldString, OBJC_ASSOCIATION_COPY);
}

- (NSString *)placeHoldString{
    return objc_getAssociatedObject(self, &placeHoldStringKey);
}


- (void)setPlaceHoldColor:(UIColor *)placeHoldColor{
    
    if (!self.placeLabel) {
        
        self.placeLabel = [self setupCustomPlaceHoldLabel];
    }
    
    self.placeLabel.textColor = placeHoldColor;
    objc_setAssociatedObject(self, &placeHoldColorKey, placeHoldColor, OBJC_ASSOCIATION_RETAIN);
}

- (UIColor *)placeHoldColor{
    return objc_getAssociatedObject(self, &placeHoldColorKey);
}



- (void)setPlaceHoldFont:(UIFont *)placeHoldFont{
    
    if (!self.placeLabel) {
        self.placeLabel = [self setupCustomPlaceHoldLabel];
    }
    
    self.placeLabel.font = placeHoldFont;
    objc_setAssociatedObject(self, &placeHoldFontKey, placeHoldFont, OBJC_ASSOCIATION_RETAIN);
}

- (UIFont *)placeHoldFont{
    return objc_getAssociatedObject(self, &placeHoldFontKey);
}


- (UILabel *)setupCustomPlaceHoldLabel{

    UILabel *label = [[UILabel alloc] init];
    label.numberOfLines = 0;
    label.textColor = [UIColor lightGrayColor];
    label.font = self.font;
    [label sizeToFit];
    [self addSubview:label];
    [self setValue:label forKey:@"_placeholderLabel"];
    
    return label;
}