让 UILabel 垂直方向顶端对齐的代码

UILabel 里放入多行文字，会发现 label 默认居中对齐，很不符合左对齐的传统习惯，下面这段 CocoaChina 版主“angellixf”分享的代码可以让 UILabel 以垂直方向顶端对齐，也就是我们常说的左对齐或右对齐

//
//  VerticallyAlignedLabel.h
//

#import <Foundation/Foundation.h>


typedef enum VerticalAlignment {
    VerticalAlignmentTop,
    VerticalAlignmentMiddle,
    VerticalAlignmentBottom,
} VerticalAlignment;

@interface VerticallyAlignedLabel : UILabel {
@private
    VerticalAlignment verticalAlignment_;
}

@property (nonatomic, assign) VerticalAlignment verticalAlignment;

@end


//
//  VerticallyAlignedLabel.m
//

#import "VerticallyAlignedLabel.h"


@implementation VerticallyAlignedLabel

@synthesize verticalAlignment = verticalAlignment_;

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        self.verticalAlignment = VerticalAlignmentMiddle;
    }
    return self;
}

- (void)setVerticalAlignment:(VerticalAlignment)verticalAlignment {
    verticalAlignment_ = verticalAlignment;
    [self setNeedsDisplay];
}

- (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines {
    CGRect textRect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines];
    switch (self.verticalAlignment) {
        case VerticalAlignmentTop:
            textRect.origin.y = bounds.origin.y;
            break;
        case VerticalAlignmentBottom:
            textRect.origin.y = bounds.origin.y + bounds.size.height - textRect.size.height;
            break;
        case VerticalAlignmentMiddle:
            // Fall through.
        default:
            textRect.origin.y = bounds.origin.y + (bounds.size.height - textRect.size.height) / 2.0;
    }
    return textRect;
}

-(void)drawTextInRect:(CGRect)requestedRect {
    CGRect actualRect = [self textRectForBounds:requestedRect limitedToNumberOfLines:self.numberOfLines];
    [super drawTextInRect:actualRect];
}

@end

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