遍历一个数组看谁快

参赛选手 ForLoop, For - in, enumerateObjectsUsingBlock这个三个方法:

    NSMutableArray *test = [NSMutableArray array];

    for (int i = 0; i < 1000000; i ++) {

        [test addObject:@(i)];

    }

    __block int sum = 0;

    double date_s = CFAbsoluteTimeGetCurrent();

    for (int i = 0; i < test.count; i ++) {

        sum += [test[i] integerValue];

    }

    double date_current = CFAbsoluteTimeGetCurrent() - date_s;

    NSLog(@"Sum : %d ForLoop Time: %f ms",sum,date_current * 1000);

    sum = 0;

    date_s = CFAbsoluteTimeGetCurrent();

    for (NSNumber *num in test) {

        sum += [num integerValue];

    }

    date_current = CFAbsoluteTimeGetCurrent() - date_s;

    NSLog(@"Sum : %d For-in Time: %f ms",sum,date_current * 1000);

    sum = 0;

    date_s = CFAbsoluteTimeGetCurrent();

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

        sum += [obj integerValue];

    }];

    date_current = CFAbsoluteTimeGetCurrent() - date_s;

    NSLog(@"Sum : %d enumrateBlock Time: %f ms",sum,date_current * 1000);

最后输出如下:

• For-in方法最快速

  结论:

  当只是遍历一个数组的时候使用For-in会比较快速, 推荐使用For-in遍历数组.

通过Value查找Index看谁快

假如现在我们要查找一个Value, 这个Value 值是100001, 找出它的index (数组的序列号).

那么现在我们来比较一下
参赛选手 For - in, enumerateObjectsUsingBlock, enumerateObjectsWithOptions 这个三个方法: (ForLoop已经不再继续讨论了）

    NSMutableArray *test = [NSMutableArray array];

    for (int i = 0; i < 10000000; i ++) {

        [test addObject:@(i + 10)];

    }

    //For-in

    __block NSInteger index = 0;

    double date_s = CFAbsoluteTimeGetCurrent();

    for (NSNumber *num in test) {

        if ([num integerValue] == 9999999) {

            index = [test indexOfObject:num];

            break;

        }

    }

    double date_current = CFAbsoluteTimeGetCurrent() - date_s;

    NSLog(@"index : %ld For-in Time: %f ms",(long)index,date_current * 1000);

    //enumerateObjectsUsingBlock

    index = 0;

    date_s = CFAbsoluteTimeGetCurrent();

    [test enumerateObjectsUsingBlock:^(id num, NSUInteger idx, BOOL *stop) {

        if ([num integerValue] == 9999999) {

            index = idx;

            *stop = YES;

        }

    }];

    date_current = CFAbsoluteTimeGetCurrent() - date_s;

    NSLog(@"index : %ld enumerateBlock Time: %f ms",(long)index,date_current * 1000);

    //enumerateObjectsWithOptions

    index = 0;

    date_s = CFAbsoluteTimeGetCurrent();

    [test enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id num, NSUInteger idx, BOOL *stop) {

        if ([num integerValue] == 9999999) {

            index = idx;

            *stop = YES;

        }

    }];

    date_current = CFAbsoluteTimeGetCurrent() - date_s;

    NSLog(@"index : %ld enumerateObjectsWithOptions Time: %f ms",(long)index,date_current * 1000);

最后输出如下图:

• enumerateObjectsWithOptions方法最快速

  结论:

  通过Value查询index的时候, 面对大量的数组推荐使用 enumerateObjectsWithOptions的并行方法.
  For-in和enumerateObjectsWithOptions方法这里我比较喜欢第二种写法简洁直观.

现在咱们要遍历字典

这里我们比较一下使用 For-in 和 enumerateKeysAndObjectsUsingBlock 这个两个方法:

    NSDictionary *testDictionary = @{

                                     @"Auther" : @"yyyyy",

                                     @"Game" : @"Dota",

                                     @"App" : @"dddddd",

                                     @"Market" : @"AppStore"

                                    };

    //For - in

    NSMutableArray *forInArry = [NSMutableArray array];

    double date_s = CFAbsoluteTimeGetCurrent();

    NSArray *keys = [testDictionary  allKeys];

    for (NSString *key in keys) {

        NSString *Value = testDictionary[key];

        [forInArry addObject:Value];

    }

    double date_current = CFAbsoluteTimeGetCurrent() - date_s;

    NSLog(@"index : %ld For-in Time: %f ms",(long)index,date_current * 1000);

    //enumerateKeysAndObjectsUsingBlock

    date_s = CFAbsoluteTimeGetCurrent();

    NSMutableArray *enumArry = [NSMutableArray array];

    [testDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {

        [enumArry addObject:obj];

    }];

    date_current = CFAbsoluteTimeGetCurrent() - date_s;

    NSLog(@"index : %ld For-in Time: %f ms",(long)index,date_current * 1000);

    NSLog(@"ForInArr: %@",forInArry);

    NSLog(@"enumArry: %@",enumArry);

打印输出:

• enumerateKeysAndObjectsUsingBlock胜出

  结论:

  当我们想遍历字典类型的时候, 推荐使用enumerateKeysAndObjectsUsingBlock
  不仅仅是因为速度快, 更是因为代码更优雅和直观.