关于EnumerateObjectsUsingBlock和for-in之间的较量
如果我们要遍历一个数组, 上过编程课程的童鞋都会想到For语句去循环.
Objective C 提供一个Block的遍历方法, 那么用它还是用For好呢？
下面我们去实践一下:
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 = [NSMutableArrayarray];for(inti =0; i <1000000; i ++) { [test addObject:@(i)]; } __blockintsum =0;doubledate_s =CFAbsoluteTimeGetCurrent();for(inti =0; i < test.count; i ++) { sum += [test[i] integerValue]; }doubledate_current =CFAbsoluteTimeGetCurrent() - date_s;NSLog(@"Sum : %d ForLoop Time: %f ms",sum,date_current *1000); sum =0; date_s =CFAbsoluteTimeGetCurrent();for(NSNumber*numintest) { 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:^(idobj,NSUIntegeridx,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:
打印输出
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 = [NSMutableArrayarray];for(inti =0; i <10000000; i ++) { [test addObject:@(i +10)]; }//For-in__blockNSIntegerindex =0;doubledate_s =CFAbsoluteTimeGetCurrent();for(NSNumber*numintest) {if([num integerValue] ==9999999) { index = [test indexOfObject:num];break; } }doubledate_current =CFAbsoluteTimeGetCurrent() - date_s;NSLog(@"index : %ld For-in Time: %f ms",(long)index,date_current *1000);//enumerateObjectsUsingBlockindex =0; date_s =CFAbsoluteTimeGetCurrent(); [test enumerateObjectsUsingBlock:^(idnum,NSUIntegeridx,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);//enumerateObjectsWithOptionsindex =0; date_s =CFAbsoluteTimeGetCurrent(); [test enumerateObjectsWithOptions:NSEnumerationConcurrentusingBlock:^(idnum,NSUIntegeridx,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:
打印输出
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 - inNSMutableArray*forInArry = [NSMutableArrayarray];doubledate_s =CFAbsoluteTimeGetCurrent();NSArray*keys = [testDictionary allKeys];for(NSString*keyinkeys) {NSString*Value = testDictionary[key]; [forInArry addObject:Value]; }doubledate_current =CFAbsoluteTimeGetCurrent() - date_s;NSLog(@"index : %ld For-in Time: %f ms",(long)index,date_current *1000);//enumerateKeysAndObjectsUsingBlockdate_s =CFAbsoluteTimeGetCurrent();NSMutableArray*enumArry = [NSMutableArrayarray]; [testDictionary enumerateKeysAndObjectsUsingBlock:^(idkey,idobj,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:
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.
http://blog.csdn.net/scboyhj__/article/details/51397104
转自这里