.h文件

#import <UIKit/UIKit.h>

@class LXFVerificationCodeView;

@protocol LXFVerificationCodeViewDelegate <NSObject>

- (void) verificationCodeViewDidChange:(LXFVerificationCodeView *) verificationCodeView;

@end
@interface LXFVerificationCodeView : UIView

@property (nonatomic, weak) id<LXFVerificationCodeViewDelegate> delegate;

//验证码范围的数组
@property (nonatomic, retain) NSArray *changeArray;
//获取后的验证码
@property (nonatomic, retain) NSMutableString *changeString;
@end

.m文件

#import "LXFVerificationCodeView.h"

@implementation LXFVerificationCodeView

#pragma mark - 初始化
- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
        
        self.layer.cornerRadius = 5.0;
        self.layer.masksToBounds = YES;
        self.backgroundColor = [UIColor blueColor];
        
        [self change];
    }
    return self;
}

#pragma mark - 点击改变验证码
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self change];
    
    if ([_delegate respondsToSelector:@selector(verificationCodeViewDidChange:)]) {
        [_delegate verificationCodeViewDidChange:self];
    }
    
    //刷新背景
    [self setNeedsDisplay];
}

#pragma mark - 随机获取验证码
- (void)change
{
    //范围
    self.changeArray = [[NSArray alloc] initWithObjects:@"0",@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"A",@"B",@"C",@"D",@"E",@"F",@"G",@"H",@"I",@"J",@"K",@"L",@"M",@"N",@"O",@"P",@"Q",@"R",@"S",@"T",@"U",@"V",@"W",@"X",@"Y",@"Z",@"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",@"i",@"j",@"k",@"l",@"m",@"n",@"o",@"p",@"q",@"r",@"s",@"t",@"u",@"v",@"w",@"x",@"y",@"z",nil];
    
    NSMutableString *getStr = [[NSMutableString alloc] initWithCapacity:5];
    
    //随机字
    self.changeString = [[NSMutableString alloc] initWithCapacity:6];
    for(NSInteger i = 0; i < 4; i++)
    {
        NSInteger index = arc4random() % ([self.changeArray count] - 1);
        getStr = [self.changeArray objectAtIndex:index];
        
        self.changeString = (NSMutableString *)[self.changeString stringByAppendingString:getStr];
    }
}

#pragma mark - 随机背景，随机颜色
- (void)drawRect:(CGRect)rect {
    [super drawRect:rect];
    //背景颜色
    float red = arc4random() % 100 / 100.0;
    float green = arc4random() % 100 / 100.0;
    float blue = arc4random() % 100 / 100.0;
    UIColor *color = [UIColor colorWithRed:red green:green blue:blue alpha:1.0];
    [self setBackgroundColor:color];
    
    NSString *text = [NSString stringWithFormat:@"%@",self.changeString];
    
    NSMutableDictionary *attrDict = [NSMutableDictionary dictionary];
    attrDict[NSFontAttributeName] = [UIFont systemFontOfSize:14];
    CGSize cSize = [@"S" sizeWithAttributes:attrDict];
   
    int width = rect.size.width / text.length - cSize.width;
    int height = rect.size.height - cSize.height;
    CGPoint point;
    
    //字体的尺寸
    float pX, pY;
    for (int i = 0; i < text.length; i++)
    {
        pX = arc4random() % width + rect.size.width / text.length * i;
        pY = arc4random() % height;
        point = CGPointMake(pX, pY);
        unichar c = [text characterAtIndex:i];
        NSString *textC = [NSString stringWithFormat:@"%C", c];
        NSMutableDictionary *attriDict = [NSMutableDictionary dictionary];
        attrDict[NSFontAttributeName] = [UIFont systemFontOfSize:20];
        [textC drawAtPoint:point withAttributes:attriDict];
    }
    
    //划线
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetLineWidth(context, 1.0);
    for(int cout = 0; cout < 10; cout++)
    {
        red = arc4random() % 100 / 100.0;
        green = arc4random() % 100 / 100.0;
        blue = arc4random() % 100 / 100.0;
        color = [UIColor colorWithRed:red green:green blue:blue alpha:1.0];
        CGContextSetStrokeColorWithColor(context, [color CGColor]);
        pX = arc4random() % (int)rect.size.width;
        pY = arc4random() % (int)rect.size.height;
        CGContextMoveToPoint(context, pX, pY);
        pX = arc4random() % (int)rect.size.width;
        pY = arc4random() % (int)rect.size.height;
        CGContextAddLineToPoint(context, pX, pY);
        CGContextStrokePath(context);
    }
}

- (void)setChangeString:(NSMutableString *)changeString{
    _changeString = changeString;
    [self setNeedsDisplay];
}
@end