iOS闪退错误定位记

1，代码为：

NSMutableArray *array = [NSMutableArray array];
    [array addObject:@" "];
    [array addObject:@" "];
    [array addObject:@" "];
    [array removeObjectAtIndex:5];

崩溃为：
Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM removeObjectsInRange:]: range {5, 1} extends beyond bounds [0 .. 2]'
解析：数字5是removeObjectAtIndex的下标，[0 .. 2]是数组里有从0到2一共3个元素。
解决办法：

- (void)removeObjectAtSafeIndex:(NSUInteger)index
{
    if (index < self.count)
    {
        [self removeObjectAtIndex:index];
    }
}

方法写成类目，然后调用这个方法移除元素

2，代码为：

NSMutableArray *array = [NSMutableArray array];
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        for (int i = 0; i < 1000; i++) {
            [array addObject:@"1"];
            NSLog(@"%d",i);
        }
    });
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        for (int i = 0; i < 100; i++) {
            for (NSString *str in array) {
                NSLog(@"%@",str);
            }
            /*for (int i = 0; i < array.count; i++) {
                NSLog(@"%@",array[i]);
            }*/
            /*[array enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
                NSLog(@"%@",obj);
            }];*/
        }
    });

崩溃为：
Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection <__NSArrayM: 0x17004e670> was mutated while being enumerated.'
解析：用for in 进行遍历其间如果修改了数组（增加或删除元素）会引起闪退
解决：用array.copy来遍历或用注释中的两种方式