placeholder垂直居中（解决光标居中、文字不居中问题）

placeholder垂直居中

解决光标居中、字体不居中问题。

问题如图：

textField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter

解决：

#import <UIKit/UIKit.h>

@interface PlaceholderVerticalAlignment : UITextField

@end

#import "PlaceholderVerticalAlignment.h"

@implementation PlaceholderVerticalAlignment

- (void)drawPlaceholderInRect:(CGRect)rect {
[super drawPlaceholderInRect:CGRectMake(0, <span style="color:#ff0000;">self.bounds.size.height * 0.5 - 0.5</span> , 0, 0)];
}

@end

[[PlaceholderVerticalAlignment alloc] initWithFrame:CGRectMake()