UILabel 垂直对齐

新建 UILabel 子类，重写部分 UILabel 方法

RYVerticalAlignmentLabel.h

typedef NS_ENUM(NSUInteger, RYTextVerticalAlignment) {
    RYTextVerticalAlignmentTop = 0, // 顶部对齐
    RYTextVerticalAlignmentMiddle,  // 垂直居中
    RYTextVerticalAlignmentBottom   // 底部对齐
};

IB_DESIGNABLE
@interface RYVerticalAlignmentLabel : UILabel

#if TARGET_INTERFACE_BUILDER
@property (nonatomic, assign) IBInspectable NSUInteger textVerticalAlignment;
#else
@property (nonatomic, assign) RYTextVerticalAlignment textVerticalAlignment;
#endif

@end

RYVerticalAlignmentLabel.m

@implementation RYVerticalAlignmentLabel

/**
 设置文本垂直对齐方式后调用 setNeedsDisplay ，系统会自动调用 drawTextInRect

 @param textVerticalAlignment 垂直对齐方式枚举类型
 */
- (void)setVerticalAlignment:(RYTextVerticalAlignment)textVerticalAlignment {
    _textVerticalAlignment = textVerticalAlignment;
    [self setNeedsDisplay];
}

/**
 重写父类 textRectForBounds 方法，修改并返回 textRect

 @param bounds 文本 bounds
 @param numberOfLines 行数
 @return 修改后文本 bounds
 */
- (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines {
    CGRect textRect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines];
    switch (self.textVerticalAlignment) {
        case RYTextVerticalAlignmentTop:
            textRect.origin.y = bounds.origin.y;
            break;
        case RYTextVerticalAlignmentBottom:
            textRect.origin.y = bounds.origin.y + bounds.size.height - textRect.size.height;
            break;
        case RYTextVerticalAlignmentMiddle:
        default:
            textRect.origin.y = bounds.origin.y + (bounds.size.height - textRect.size.height) / 2.0;
    }
    return textRect;
}

/**
  重写父类 drawTextInRect 方法，调用本类 textRectForBounds 方法

 @param requestedRect 文本 bounds
 */
-(void)drawTextInRect:(CGRect)requestedRect {
    CGRect actualRect = [self textRectForBounds:requestedRect limitedToNumberOfLines:self.numberOfLines];
    [super drawTextInRect:actualRect];
}

@end

IBInspectable

IBInspectable关键字，可以使自定义 UIView 的属性出现在 IB 中的 Attributes inspector

如 RYVerticalAlignmentLabel.h 中为对应属性添加关键字

#if TARGET_INTERFACE_BUILDER
@property (nonatomic, assign) IBInspectable NSUInteger textVerticalAlignment;
#else
@property (nonatomic, assign) RYTextVerticalAlignment textVerticalAlignment;
#endif

在 xib / storyboard 中拖入 UIlabel 对象视图后，修改 Class

效果

IB_DESIGNABLE

IB_DESIGNABLE关键字 可以让自定义 UIView 在 IB 中预览

如 RYVerticalAlignmentLabel.h 中为类添加关键字

IB_DESIGNABLE
@interface RYVerticalAlignmentLabel : UILabel

效果

参考

[爆栈热门 iOS 问题] 让 UILabel 顶端对齐

IB_DESIGNABLE 和 IBInspectable 的用法