2.1、iOS_数组遍历

数组的五种遍历

首先定义一个数组，并获取数组长度

    NSArray *array=@[@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",];

    NSInteger count =array.count;

一、for循环

for (NSInteger i=0; i

  NSLog(@"%@----%@",array[i],[NSThread currentThread]);

}

打印结果如下：

1

2

 3

4

。。。。

二、for in 快速枚举

for (NSString *string in array) {

        NSLog(@"%@----%@",string,[NSThread currentThread]);

}

打印结果如下：

2017-01-03 11:04:01.990 MyTestWorkProduct[2086:78292] 1----{number = 1, name = main}

2017-01-03 11:04:01.990 MyTestWorkProduct[2086:78292] 2----{number = 1, name = main}

2017-01-03 11:04:01.991 MyTestWorkProduct[2086:78292] 3----{number = 1, name = main}

2017-01-03 11:04:01.992 MyTestWorkProduct[2086:78292] 4----{number = 1, name = main}

2017-01-03 11:04:01.992 MyTestWorkProduct[2086:78292] 5----{number = 1, name = main}

2017-01-03 11:04:01.993 MyTestWorkProduct[2086:78292] 6----{number = 1, name = main}

2017-01-03 11:04:01.993 MyTestWorkProduct[2086:78292] 7----{number = 1, name = main}

2017-01-03 11:04:01.993 MyTestWorkProduct[2086:78292] 8----{number = 1, name = main}

2017-01-03 11:04:01.994 MyTestWorkProduct[2086:78292] 9----{number = 1, name = main}

2017-01-03 11:04:01.994 MyTestWorkProduct[2086:78292] end

三、NSEnumerator

NSEnumerator *enumer=[array objectEnumerator];

    id obj;

    while (obj=[enumer nextObject]) {

        NSLog(@"%@----%@",obj,[NSThread currentThread]);

    }

打印结果如下：

2017-01-03 11:05:37.138 MyTestWorkProduct[2156:79788] 1----{number = 1, name = main}

2017-01-03 11:05:37.139 MyTestWorkProduct[2156:79788] 2----{number = 1, name = main}

2017-01-03 11:05:37.140 MyTestWorkProduct[2156:79788] 3----{number = 1, name = main}

2017-01-03 11:05:37.140 MyTestWorkProduct[2156:79788] 4----{number = 1, name = main}

2017-01-03 11:05:37.140 MyTestWorkProduct[2156:79788] 5----{number = 1, name = main}

2017-01-03 11:05:37.141 MyTestWorkProduct[2156:79788] 6----{number = 1, name = main}

2017-01-03 11:05:37.141 MyTestWorkProduct[2156:79788] 7----{number = 1, name = main}

2017-01-03 11:05:37.141 MyTestWorkProduct[2156:79788] 8----{number = 1, name = main}

2017-01-03 11:05:37.142 MyTestWorkProduct[2156:79788] 9----{number = 1, name = main}

2017-01-03 11:05:37.142 MyTestWorkProduct[2156:79788] end

四、快速遍历

//顺序遍历

    [array enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {

        NSLog(@"%@----%@",array[idx],[NSThread currentThread]);

    }];

    //倒序遍历

    [array enumerateObjectsWithOptions:NSEnumerationReverse usingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {

        NSLog(@"%@----%@",array[idx],[NSThread currentThread]);

    }];

打印结果如下：

1

2

 3

4

.....

4

3

2

1

五、快速迭代

//将block中的任务，逐个放到queue中，然后进行dispatch_sync执行

    //多线程同步循环

    dispatch_queue_t queue =dispatch_queue_create("apply并行队列", DISPATCH_QUEUE_CONCURRENT);

    dispatch_apply(count, queue, ^(size_t index) {

        NSLog(@"%@----%@",array[index],[NSThread currentThread]);

    });

      NSLog(@"end");

打印结果如下：

1

7

6

8

1

1

7

6

8

1

根据打印结果最后才打印 end 字符可知，dispatch_apply会等待每个block中的任务都执行完成后，才往下执行。

总结：从这五种遍历方式来看，第5种采用的多线程，对于处理耗时的数组遍历比较适用。