我们经常会在手机应用中会看到输入验证码，然后操作一个东西，那么我们应该如何去实现他呢，先看一下效果

verificationCode.gif

1、首先我们定义一个继承 UIView 的类 ZYCaptchaView 用于、生成验证码的操作

2、 .h 文件中我们这样声明

/**字符数组 */
@property (nonatomic , strong)NSArray *characterArray;
/** 验证码字符串 */
@property (nonatomic , strong)NSMutableString  *captchaString;
 /** 加载验证码 */
- (void)loadCaptcha;

3、 .m 文件中我们具体去实现

首先，我们在 initWithFrame 中生成一个随机的验证码

- (instancetype)initWithFrame:(CGRect)frame {
if (self = [super initWithFrame:frame]) {
    //设置layer圆角半径
    self.layer.cornerRadius = 5.0;
    //影藏边境
    self.layer.masksToBounds = YES;
    self.backgroundColor = kRandomColor;
    //显示一个随机验证码
    [self randomCaptcha];
}
return self;
}
 #pragma mark -- 更换验证码
- (void)randomCaptcha {
//数组中存放的是全部可选的字符，可以是字母，也可以是中文
self.characterArray = [[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:kCharCount];
self.captchaString = [[NSMutableString alloc] initWithCapacity:kCharCount];
//随机从数组中选取需要个数的字符，然后拼接为一个字符串
for (int i = 0 ; i < kCharCount; i ++) {
    int index = arc4random() % (self.characterArray.count - 1);
    getStr = [self.characterArray objectAtIndex:index];
    self.captchaString = [[self.captchaString stringByAppendingString:getStr] copy];
}
//从网络获取字符串，然后把得到的字符串在本地绘制出来（网络获取步骤在这省略）
}

其次，我们实现加载验证码的代码

/** 加载验证码 */
- (void)loadCaptcha {
   //更换验证码
 [self randomCaptcha];
//重新绘制
[self setNeedsDisplay];
}

最后我们实现绘制验证码的代码,也就是重写 drawRect 方法

#pragma mark 绘制界面
- (void)drawRect:(CGRect)rect {
[super drawRect:rect];
//设置随机背景颜色
self.backgroundColor = kRandomColor;
//获取要显示的验证码字符串
NSString *text = [NSString stringWithFormat:@"%@" , self.captchaString];
CGSize cSize = [@"s" sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:20]}];
int width = rect.size.width / text.length - cSize.width;
int height = rect.size.height - cSize.height;
CGPoint point;
//依次绘制每一个字符,可以设置显示的每个字符的字体大小、颜色、样式等
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];
    [textC drawAtPoint:point withAttributes:@{NSFontAttributeName:kFontSize}];
}
//获取上下文
CGContextRef context = UIGraphicsGetCurrentContext();
//设置画线宽度
CGContextSetLineWidth(context, kLineWidth);
//绘制干扰的彩色直线
for (int i = 0; i < kLineCount; i ++) {
    //设置线的随机颜色
    UIColor *color = kRandomColor;
    CGContextSetStrokeColorWithColor(context, color.CGColor);
    //设置线的起点
    pX = arc4random() % (int)rect.size.width;
    pY = arc4random() % (int)rect.size.height;
    CGContextMoveToPoint(context, pX, pY);
    //设置线的终点
    pX = arc4random() % (int)rect.size.width;
    pY = arc4random() % (int)rect.size.height;
    CGContextAddLineToPoint(context, pX, pY);
    //画线
    CGContextStrokePath(context);
  }
}

4、在控制器中调用我们的类

需要注意的是我们需要让验证码不区分大小写，我们就需要大小写进行转换，你可以将所有字母转换为大写，也可以转换为小写。大小写转换的代码如下：

/** 大写字母转换为小写 */
- (NSString *)toLower:(NSString *)str {
for (int i = 0; i < str.length; i++) {
    if ([str characterAtIndex:i] >= 'A' && [str characterAtIndex:i] <= 'Z') {
        char temp = [str characterAtIndex:i] + 32;
        NSRange range = NSMakeRange(i, 1);
        str = [str stringByReplacingCharactersInRange:range withString:[NSString stringWithFormat:@"%c" , temp]];
    }
}
return str;
}
/** 小写字母转换为大写 */
-(NSString *)toUpper:(NSString *)str{
for (int i = 0; i < str.length; i++) {
    if ([str characterAtIndex:i]>='a'&[str characterAtIndex:i]<='z') {
        char  temp=[str characterAtIndex:i]-32;
        NSRange range=NSMakeRange(i, 1);
        str=[str stringByReplacingCharactersInRange:range withString:[NSString stringWithFormat:@"%c",temp]];
    }
}
return str;
}

大概就这些步骤了，如有需