was mutated while being enumerated.

又一次写验证码demo的时候，一下代码carsh了

[self.qBgView.layer.sublayers enumerateObjectsUsingBlock:^(CALayer * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
if ([obj isKindOfClass:[CAShapeLayer class]]) {
[obj removeFromSuperlayer];
}

}];

carsh原因： reason: ‘* Collection was mutated while being enumerated.’

翻译下来就是“一边遍历集合，一边又修改集合里面的内容，导致崩溃”，

将以上代码修改成以下的就可以了：

NSMutableArray *layerArr = [self.qBgView.layer.sublayers mutableCopy];
[layerArr enumerateObjectsUsingBlock:^(CALayer * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
if ([obj isKindOfClass:[CAShapeLayer class]]) {
[obj removeFromSuperlayer];
}

}];