标签：
ForLoop, For - in, enumerateObjects这个三个方法的区别:遍历一个数组用For-in最快.
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.
遍历字典类型的时候, enumerateKeysAndObjectsUsingBlock效率最高
1.1遍历数组
NSMutableArray *test = [NSMutableArray array]; for (int i = 0; i < 1000000; i ++) { [test addObject:@(i)]; } //ForLoop方法 __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); //For - in方法 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); //enumerateObjectsUsingBlock方法 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);
打印如下:
总结:遍历一个数组用For-in最快.
1.2-通过Value查找Index看谁快
实验: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);
打印:
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.
1.3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" }; NSMutableArray *forInArry1 = [NSMutableArray array]; NSMutableArray *forInArry2 = [NSMutableArray array]; NSMutableArray *enumArry = [NSMutableArray array]; //For - in方法 直接allValues double date_s = CFAbsoluteTimeGetCurrent(); NSArray *values = testDictionary.allValues; for (NSString *value in values) { [forInArry1 addObject:value]; } double date_current = CFAbsoluteTimeGetCurrent() - date_s; NSLog(@"index : %ld For-in-forInArry1 Time: %f ms",(long)index,date_current * 1000); //For - in方法,+根据key取value值 date_s = CFAbsoluteTimeGetCurrent(); NSArray *keys = testDictionary.allKeys; for (NSString *key in keys) { NSString *Value = testDictionary[key]; [forInArry2 addObject:Value]; } date_current = CFAbsoluteTimeGetCurrent() - date_s; NSLog(@"index : %ld For-in-forInArry2 Time: %f ms",(long)index,date_current * 1000); //enumerateKeysAndObjectsUsingBlock方法. date_s = CFAbsoluteTimeGetCurrent(); [testDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) { [enumArry addObject:obj]; }]; date_current = CFAbsoluteTimeGetCurrent() - date_s; NSLog(@"index : %ld enumerateKeysAndObjectsUsingBlock Time: %f ms",(long)index,date_current * 1000);
打印:
结论:遍历字典类型的时候, enumerateKeysAndObjectsUsingBlock效率最高
标签：
原文地址：http://www.cnblogs.com/jiayongqiang/p/5596154.html
