oc-UITextView占位文字及占位文字颜色扩展(可在xib中直接使用)

使用案例

.h文件

```

#import <UIKit/UIKit.h>

 

// 在定义类的前面加上IB_DESIGNABLE宏

IB_DESIGNABLE // 动态刷新

NS_ASSUME_NONNULL_BEGIN

 

@interface UITextView (HWCategory)

@property (nonatomic, strong) IBInspectable NSString *placeholder;

@property (nonatomic, strong) IBInspectable UIColor *placeholderColor;

 

@end

 

 

NS_ASSUME_NONNULL_END

```

 

.m文件

```

#import "UITextView+HWCategory.h"

#import <objc/runtime.h>

 

static NSString const *placeholderKey = @"placeholderKey";

static NSString const *placeholderLabelKey = @"placeholderLabelKey";

@implementation UITextView (HWCategory)

- (void)setPlaceholder:(NSString *)placeholder {

    objc_setAssociatedObject(self, (__bridge const void * _Nonnull)(placeholderKey), placeholder, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

    if (![self.subviews containsObject:self.placeholderLabel]) {

        [self getPlaceholderLabel];

        self.placeholderLabel.text = placeholder;

    } else {

        self.placeholderLabel.text = placeholder;

    }

}

- (void)setPlaceholderColor:(UIColor *)placeholderColor {

    if (![self.subviews containsObject:self.placeholderLabel]) { return; }

    self.placeholderLabel.textColor = placeholderColor;

}

- (UIColor *)placeholderColor {

    return self.placeholderLabel.textColor;

}

- (NSString *)placeholder {

    return objc_getAssociatedObject(self, (__bridge const void * _Nonnull)(placeholderKey));

}

- (void)setPlaceholderLabel:(UILabel *)placeholderLabel {

    objc_setAssociatedObject(self, (__bridge const void * _Nonnull)(placeholderLabelKey), placeholderLabel, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

}

 

- (UILabel *)placeholderLabel {

    id label = objc_getAssociatedObject(self, (__bridge const void * _Nonnull)(placeholderLabelKey));

    if (!label) {

        [self getPlaceholderLabel];

    }

    return label;

}

- (UILabel *)getPlaceholderLabel {

    if (!self.font) {

        self.font = [UIFont systemFontOfSize:14];

    }

    UILabel *lab = [[UILabel alloc] initWithFrame:self.bounds];

    lab.numberOfLines = 0;

    lab.font = self.font;

    lab.textColor = [UIColor lightGrayColor];

    [self addSubview:lab];

    [self setValue:lab forKey:@"_placeholderLabel"];

    [self setPlaceholderLabel:lab];

    [self sendSubviewToBack:self.placeholderLabel];

    return lab;

}

@end

```