iOS開發中數組經常使用的五種遍歷方式

隨着iOS的不斷髮展，apple也不斷推出性能更高的數組遍歷方式，下面將對熟悉的五種遍歷方式進行列舉。

首先定義一個數組，並獲取數組長度

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

1、for循環

for (NSInteger i=0; i<count; i++) {
   NSLog(@"%@----%@",array[i],[NSThread currentThread]);
}

打印結果以下：
2017-01-03 11:02:01.537 MyTestWorkProduct[2013:76489] 1----<NSThread: 0x600000260e80>{number = 1, name = main}
2017-01-03 11:02:01.538 MyTestWorkProduct[2013:76489] 2----<NSThread: 0x600000260e80>{number = 1, name = main}
2017-01-03 11:02:01.539 MyTestWorkProduct[2013:76489] 3----<NSThread: 0x600000260e80>{number = 1, name = main}
2017-01-03 11:02:01.539 MyTestWorkProduct[2013:76489] 4----<NSThread: 0x600000260e80>{number = 1, name = main}
2017-01-03 11:02:01.539 MyTestWorkProduct[2013:76489] 5----<NSThread: 0x600000260e80>{number = 1, name = main}
2017-01-03 11:02:01.540 MyTestWorkProduct[2013:76489] 6----<NSThread: 0x600000260e80>{number = 1, name = main}
2017-01-03 11:02:01.540 MyTestWorkProduct[2013:76489] 7----<NSThread: 0x600000260e80>{number = 1, name = main}
2017-01-03 11:02:01.540 MyTestWorkProduct[2013:76489] 8----<NSThread: 0x600000260e80>{number = 1, name = main}
2017-01-03 11:02:01.541 MyTestWorkProduct[2013:76489] 9----<NSThread: 0x600000260e80>{number = 1, name = main}
2017-01-03 11:02:01.541 MyTestWorkProduct[2013:76489] end

2、forin 快速枚舉

 for (NSString *string in array) {
        NSLog(@"%@----%@",string,[NSThread currentThread]);
 }

打印結果以下：
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

3、NSEnumerator

 NSEnumerator *enumer=[array objectEnumerator];
    id obj;
    while (obj=[enumer nextObject]) {
        NSLog(@"%@----%@",obj,[NSThread currentThread]);
    }
打印結果以下：
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

4、快速遍歷

//順序遍歷
    [array enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"%@----%@",array[idx],[NSThread currentThread]);
    }];
    //倒序遍歷
    [array enumerateObjectsWithOptions:NSEnumerationReverse usingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"%@----%@",array[idx],[NSThread currentThread]);
    }];
打印結果以下：
2017-01-03 11:07:30.774 MyTestWorkProduct[2229:81188] 1----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.775 MyTestWorkProduct[2229:81188] 2----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.775 MyTestWorkProduct[2229:81188] 3----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.776 MyTestWorkProduct[2229:81188] 4----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.777 MyTestWorkProduct[2229:81188] 5----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.778 MyTestWorkProduct[2229:81188] 6----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.778 MyTestWorkProduct[2229:81188] 7----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.779 MyTestWorkProduct[2229:81188] 8----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.779 MyTestWorkProduct[2229:81188] 9----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.780 MyTestWorkProduct[2229:81188] 9----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.781 MyTestWorkProduct[2229:81188] 8----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.781 MyTestWorkProduct[2229:81188] 7----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.782 MyTestWorkProduct[2229:81188] 6----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.782 MyTestWorkProduct[2229:81188] 5----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.783 MyTestWorkProduct[2229:81188] 4----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.784 MyTestWorkProduct[2229:81188] 3----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.785 MyTestWorkProduct[2229:81188] 2----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.786 MyTestWorkProduct[2229:81188] 1----<NSThread: 0x600000070240>{number = 1, name = main}
2017-01-03 11:07:30.786 MyTestWorkProduct[2229:81188] end

5、快速迭代

//將block中的任務，逐個放到queue中，而後進行dispatch_sync執行
    //多線程同步循環
    
    dispatch_queue_t queue =dispatch_queue_create("apply並行隊列", DISPATCH_QUEUE_CONCURRENT);
    dispatch_apply(count, queue, ^(size_t index) {
        NSLog(@"%@----%@",array[index],[NSThread currentThread]);
    });

      NSLog(@"end");

打印結果以下：
2017-01-03 11:09:00.114 MyTestWorkProduct[2302:82847] 1----<NSThread: 0x60000006b940>{number = 1, name = main}
2017-01-03 11:09:00.114 MyTestWorkProduct[2302:82977] 3----<NSThread: 0x600000876cc0>{number = 7, name = (null)}
2017-01-03 11:09:00.114 MyTestWorkProduct[2302:83008] 2----<NSThread: 0x600000479a80>{number = 6, name = (null)}
2017-01-03 11:09:00.114 MyTestWorkProduct[2302:83482] 4----<NSThread: 0x60800067e740>{number = 8, name = (null)}
2017-01-03 11:09:00.114 MyTestWorkProduct[2302:82847] 5----<NSThread: 0x60000006b940>{number = 1, name = main}
2017-01-03 11:09:00.115 MyTestWorkProduct[2302:82977] 6----<NSThread: 0x600000876cc0>{number = 7, name = (null)}
2017-01-03 11:09:00.115 MyTestWorkProduct[2302:83008] 7----<NSThread: 0x600000479a80>{number = 6, name = (null)}
2017-01-03 11:09:00.116 MyTestWorkProduct[2302:83482] 8----<NSThread: 0x60800067e740>{number = 8, name = (null)}
2017-01-03 11:09:00.116 MyTestWorkProduct[2302:82847] 9----<NSThread: 0x60000006b940>{number = 1, name = main}
2017-01-03 11:09:00.116 MyTestWorkProduct[2302:82847] end

根據打印結果最後纔打印 end 字符可知，dispatch_apply會等待每一個block中的任務都執行完成後，才往下執行。

總結：從這五種遍歷方式來看，第5種採用的多線程，對於處理耗時的數組遍歷比較適用。