迭代for循环时变慢

Question

for ( NSDictionary *detailsDict in rsltArray) { NSString *OfficeId =[detailsDict objectForKey:@"ObjectId"]; NSString *catID =[detailsDict objectForKey:@"catID"]; NSString *ObjType =[detailsDict objectForKey:@"ObjectType"];

        NSString *getImage = [NSString stringWithFormat:@"select catMarkericon from TBL_Category where catID='%@'",catID];
        NSMutableArray * imageArray = [self.database getDataListBySQLQueryStatement:getImage];
        NSString *officeLogo  = [[imageArray objectAtIndex:0] objectForKey:@"catMarkericon"];

        NSArray *parts = [officeLogo componentsSeparatedByString:@"/"];
        NSString *filename = [parts lastObject];


        NSString *OfficeName;
        NSString *OfficeAddress;
        if([[UserDefaults getLanguageSelection]isEqualToString:@"en"])
        {
            OfficeName  =[detailsDict objectForKey:@"ObjectNameEnglish"];
            OfficeAddress  =[detailsDict objectForKey:@"ObjectAddressEnglish"];
        }
        else
        {
            OfficeName  =[detailsDict objectForKey:@"ObjectNameArabic"];
            OfficeAddress  =[detailsDict objectForKey:@"ObjectAddressArabic"];
        }

        double Off_lat      =[[detailsDict objectForKey:@"Latitude"] doubleValue];
        double Off_long     =[[detailsDict objectForKey:@"Longitude"] doubleValue];

        tempLocation = [[CLLocation alloc] initWithLatitude:Off_lat longitude:Off_long];
        CLLocationDistance meters = [tempLocation distanceFromLocation:CurrentLoc]/1000;

        if(meters<=Dist)
        {
            [arrListdata addObject:detailsDict];
            if ([catID isEqualToString:selectID]) {
                tempCoordinate = [ARGeoMarkerco coordinateWithLocation:tempLocation locationTitle:OfficeName withid:OfficeId withaddress:OfficeAddress withimage:filename withcatId:catID withObjType:ObjType selectValue:YES newmarker:NO];
                [locationArray addObject:tempCoordinate];
            }
            else{
                tempCoordinate = [ARGeoMarkerco coordinateWithLocation:tempLocation locationTitle:OfficeName withid:OfficeId withaddress:OfficeAddress withimage:filename withcatId:catID withObjType:ObjType selectValue:NO newmarker:NO];
                [locationArray addObject:tempCoordinate];
            }

    }

}

我正在使用这样的 for 循环，我必须迭代超过 1500 个数据，并且它会在 4 到 7 秒内卡住我的应用程序是任何解决此问题的方法

Answer 1

我必须用 Objective C/pseudocode 混合来写这个，只是为了尽快给你答案。

将 1500 个成员数组拆分为 2 个。

NSRange theRange;
NSRange theSecondRange;
theRange.location = 0;
theRange.length = 749;
theSecondRange.location = 750;
theSecondRange.length = 750;    
NSArray *array1 = [rsltArray subarrayWithRange:theRange];
NSArray *array2 = [rsltArray subarrayWithRange:theSecondRange];

然后，在后台创建 2 个调度队列。使用您拥有的代码将第一个数组从第一个队列中取出。对第二个做同样的事情。线程完成后，使用 NSArray arrayByAddingObjectsFromArray 将它们放在一起。

如果仍然太慢，请将数组进一步拆分为 4 或 8 个，并将它们线程化到单独的队列中。诀窍是您必须等到线程返回后再添加它们，否则您的应用程序将崩溃，因为不会有一个数组可以添加回一个主数组。 更新请参阅 Apple 上的此链接，了解 Grand Central Dispatch 中的调度组，以处理我提到的子阵列何时返回 https://developer.apple.com/library/ios/documentation/Performance/Reference/GCD_libdispatch_Ref/index.html#//apple_ref/doc/uid/TP40008079-CH2-SW19