用for循環(huán)遍歷了可變對(duì)象，同時(shí)對(duì)可變對(duì)象進(jìn)行增加、刪除操作會(huì)報(bào)此錯(cuò)誤：

• reason: Collection <__NSArrayM: 0x60800005bd50> was mutated while being enumerated

解決辦法：

① 操作完成立刻跳出循環(huán)

NSMutableArray *array = [NSMutableArray arrayWithObjects:@"1", @"2", @"3", @"4", @"5" , nil];
    for (NSString *str in array) {
        if ([str isEqualToString:@"2"]) {
            [array removeObject:@"0"];
            break;
        }
    }
注意：用 continue 跳出還是會(huì)報(bào)錯(cuò)，必須結(jié)束循環(huán)

② 遍歷copy后的對(duì)象

for (NSString *str in [array copy]) {
        if ([str isEqualToString:@"2"]) {
            [array addObject:@"0"];
        }
    }

③ 開(kāi)線程去執(zhí)行操作

for (NSString *str in array) {
        if ([str isEqualToString:@"2"]) {
            dispatch_async(dispatch_get_global_queue(0, 0), ^{
                [array addObject:@"0"];
            });
        }
    }

④ 更換遍歷方式

[array enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        if ([obj isEqualToString:@"2"]) {
            [array removeObject:obj];
//            *stop = true;
        }
    }];

話題延伸：

@property (atomic, strong)NSMutableArray *array;
原子屬性修飾的對(duì)象是安全的，那么以上屬性是安全的嗎？

面試中可能會(huì)遇到這樣的問(wèn)題，atomic修飾只是說(shuō)此對(duì)象setter & getter 方法是安全的，對(duì)象本身并不是安全的；

@property (nonatomic, copy)NSMutableArray *array;
對(duì)這個(gè)數(shù)組進(jìn)行增加、刪除操作會(huì)報(bào)錯(cuò)嗎？

會(huì), 打印對(duì)象的類型就看到了：

@property (nonatomic, copy)NSMutableArray *array1;
@property (nonatomic, strong)NSMutableArray *array2;

NSLog(@"%@, ", [self.array1 class]);
NSLog(@"%@, ", [self.array2 class]);

2016-11-14 17:55:15.053 TestArray[26252:1532398] __NSArrayI, 
2016-11-14 17:55:15.055 TestArray[26252:1532398] __NSArrayM, 

沒(méi)有經(jīng)過(guò)copy修飾的是Mutable類型，經(jīng)過(guò)copy修飾的是Immutable類型

以上代碼均經(jīng)過(guò)測(cè)試，如有不妥的地方希望指正！