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<count; 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----<NSThread: 0x60000007a400>{number = 1, name = main}
2017-01-03 11:04:01.990 MyTestWorkProduct[2086:78292] 2----<NSThread: 0x60000007a400>{number = 1, name = main}
2017-01-03 11:04:01.991 MyTestWorkProduct[2086:78292] 3----<NSThread: 0x60000007a400>{number = 1, name = main}
2017-01-03 11:04:01.992 MyTestWorkProduct[2086:78292] 4----<NSThread: 0x60000007a400>{number = 1, name = main}
2017-01-03 11:04:01.992 MyTestWorkProduct[2086:78292] 5----<NSThread: 0x60000007a400>{number = 1, name = main}
2017-01-03 11:04:01.993 MyTestWorkProduct[2086:78292] 6----<NSThread: 0x60000007a400>{number = 1, name = main}
2017-01-03 11:04:01.993 MyTestWorkProduct[2086:78292] 7----<NSThread: 0x60000007a400>{number = 1, name = main}
2017-01-03 11:04:01.993 MyTestWorkProduct[2086:78292] 8----<NSThread: 0x60000007a400>{number = 1, name = main}
2017-01-03 11:04:01.994 MyTestWorkProduct[2086:78292] 9----<NSThread: 0x60000007a400>{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----<NSThread: 0x608000078980>{number = 1, name = main}
2017-01-03 11:05:37.139 MyTestWorkProduct[2156:79788] 2----<NSThread: 0x608000078980>{number = 1, name = main}
2017-01-03 11:05:37.140 MyTestWorkProduct[2156:79788] 3----<NSThread: 0x608000078980>{number = 1, name = main}
2017-01-03 11:05:37.140 MyTestWorkProduct[2156:79788] 4----<NSThread: 0x608000078980>{number = 1, name = main}
2017-01-03 11:05:37.140 MyTestWorkProduct[2156:79788] 5----<NSThread: 0x608000078980>{number = 1, name = main}
2017-01-03 11:05:37.141 MyTestWorkProduct[2156:79788] 6----<NSThread: 0x608000078980>{number = 1, name = main}
2017-01-03 11:05:37.141 MyTestWorkProduct[2156:79788] 7----<NSThread: 0x608000078980>{number = 1, name = main}
2017-01-03 11:05:37.141 MyTestWorkProduct[2156:79788] 8----<NSThread: 0x608000078980>{number = 1, name = main}
2017-01-03 11:05:37.142 MyTestWorkProduct[2156:79788] 9----<NSThread: 0x608000078980>{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。
